21907256121 has 27 divisors (see below), whose sum is σ = 32020867749. Its totient is φ = 14432848632.

The previous prime is 21907256093. The next prime is 21907256149. The reversal of 21907256121 is 12165270912.

The square root of 21907256121 is 148011.

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

21907256121 is a `hidden beast` number, since 2 + 1 + 9 + 0 + 72 + 561 + 21 = 666.

It is an interprime number because it is at equal distance from previous prime (21907256093) and next prime (21907256149).

It is not a de Polignac number, because 21907256121 - 2⁹ = 21907255609 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21907256171) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 45735160 + ... + 45735638.

Almost surely, 2^21907256121 is an apocalyptic number.

21907256121 is the 148011-st square number.

21907256121 is the 74006-th centered octagonal number.

It is an amenable number.

21907256121 is a deficient number, since it is larger than the sum of its proper divisors (10113611628).

21907256121 is an frugal number, since it uses more digits than its factorization.

21907256121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1170 (or 585 counting only the distinct ones).

The product of its (nonzero) digits is 15120, while the sum is 36.

Multiplying 21907256121 by its sum of digits (36), we get a square (788661220356 = 888066²).

The spelling of 21907256121 in words is "twenty-one billion, nine hundred seven million, two hundred fifty-six thousand, one hundred twenty-one".