21655015715025 has 1215 divisors, whose sum is σ = 55182036813057. Its totient is φ = 8362888934400.

The previous prime is 21655015715017. The next prime is 21655015715033. The reversal of 21655015715025 is 52051751055612.

The square root of 21655015715025 is 4653495.

It is a perfect power (a square), and thus also a powerful number.

21655015715025 is a `hidden beast` number, since 2 + 1 + 6 + 5 + 5 + 0 + 1 + 571 + 50 + 25 = 666.

It is an interprime number because it is at equal distance from previous prime (21655015715017) and next prime (21655015715033).

It can be written as a sum of positive squares in 4 ways, for example, as 506532547521 + 21148483167504 = 711711^2 + 4598748^2 .

It is not a de Polignac number, because 21655015715025 - 2³ = 21655015715017 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 1214 ways as a sum of consecutive naturals, for example, 274114122936 + ... + 274114123014.

Almost surely, 2^{21655015715025} is an apocalyptic number.

21655015715025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21655015715025 is the 4653495-th square number.

21655015715025 is the 2326748-th centered octagonal number.

It is an amenable number.

21655015715025 is an abundant number, since it is smaller than the sum of its proper divisors (33527021098032).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21655015715025 is a wasteful number, since it uses less digits than its factorization.

21655015715025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 250 (or 122 counting only the distinct ones).

The product of its (nonzero) digits is 525000, while the sum is 45.

The spelling of 21655015715025 in words is "twenty-one trillion, six hundred fifty-five billion, fifteen million, seven hundred fifteen thousand, twenty-five".