21555173990025 has 243 divisors, whose sum is σ = 43350080578077. Its totient is φ = 10233374860800.

The previous prime is 21555173989991. The next prime is 21555173990081. The reversal of 21555173990025 is 52009937155512.

The square root of 21555173990025 is 4642755.

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

21555173990025 is a `hidden beast` number, since 2 + 1 + 5 + 5 + 517 + 39 + 90 + 0 + 2 + 5 = 666.

It can be written as a sum of positive squares in 40 ways, for example, as 11675417458761 + 9879756531264 = 3416931^2 + 3143208^2 .

It is not a de Polignac number, because 21555173990025 - 2²¹ = 21555171892873 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 242 ways as a sum of consecutive naturals, for example, 26254779115 + ... + 26254779935.

Almost surely, 2^{21555173990025} is an apocalyptic number.

21555173990025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21555173990025 is the 4642755-th square number.

21555173990025 is the 2321378-th centered octagonal number.

It is an amenable number.

21555173990025 is an abundant number, since it is smaller than the sum of its proper divisors (21794906588052).

21555173990025 is an equidigital number, since it uses as much as digits as its factorization.

21555173990025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1742 (or 871 counting only the distinct ones).

The product of its (nonzero) digits is 4252500, while the sum is 54.

The spelling of 21555173990025 in words is "twenty-one trillion, five hundred fifty-five billion, one hundred seventy-three million, nine hundred ninety thousand, twenty-five".