21210307866225 has 27 divisors (see below), whose sum is σ = 37990141823179. Its totient is φ = 11312127351600.

The previous prime is 21210307866197. The next prime is 21210307866283. The reversal of 21210307866225 is 52266870301212.

The square root of 21210307866225 is 4605465.

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

21210307866225 is a `hidden beast` number, since 2 + 1 + 2 + 10 + 3 + 0 + 7 + 8 + 6 + 622 + 5 = 666.

It can be written as a sum of positive squares in only one way, i.e., 7635710831841 + 13574597034384 = 2763279^2 + 3684372^2 .

It is not a de Polignac number, because 21210307866225 - 2¹⁷ = 21210307735153 is a prime.

It is a super-2 number, since 2×21210307866225² (a number of 27 digits) contains 22 as substring.

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

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 68928460 + ... + 69235490.

Almost surely, 2^{21210307866225} is an apocalyptic number.

21210307866225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21210307866225 is the 4605465-th square number.

21210307866225 is the 2302733-rd centered octagonal number.

It is an amenable number.

21210307866225 is a deficient number, since it is larger than the sum of its proper divisors (16779833956954).

21210307866225 is an frugal number, since it uses more digits than its factorization.

21210307866225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 614078 (or 307039 counting only the distinct ones).

The product of its (nonzero) digits is 483840, while the sum is 45.

The spelling of 21210307866225 in words is "twenty-one trillion, two hundred ten billion, three hundred seven million, eight hundred sixty-six thousand, two hundred twenty-five".