21256645437 has 24 divisors (see below), whose sum is σ = 30787848000. Its totient is φ = 14132479680.

The previous prime is 21256645381. The next prime is 21256645477. The reversal of 21256645437 is 73454665212.

21256645437 is a `hidden beast` number, since 2 + 1 + 2 + 566 + 4 + 54 + 37 = 666.

It is not a de Polignac number, because 21256645437 - 2¹¹ = 21256643389 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21256645392 and 21256645401.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21256645477) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 6073314 + ... + 6076812.

It is an arithmetic number, because the mean of its divisors is an integer number (1282827000).

Almost surely, 2^21256645437 is an apocalyptic number.

It is an amenable number.

21256645437 is a deficient number, since it is larger than the sum of its proper divisors (9531202563).

21256645437 is a wasteful number, since it uses less digits than its factorization.

21256645437 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5153 (or 5150 counting only the distinct ones).

The product of its digits is 1209600, while the sum is 45.

The spelling of 21256645437 in words is "twenty-one billion, two hundred fifty-six million, six hundred forty-five thousand, four hundred thirty-seven".