21256016124645 has 144 divisors (see below), whose sum is σ = 41332302490752. Its totient is φ = 10082814044160.

The previous prime is 21256016124559. The next prime is 21256016124661. The reversal of 21256016124645 is 54642161065212.

21256016124645 is a `hidden beast` number, since 2 + 1 + 2 + 560 + 1 + 6 + 1 + 2 + 46 + 45 = 666.

It is not a de Polignac number, because 21256016124645 - 2⁷ = 21256016124517 is a prime.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21256016124645.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 24398455 + ... + 25254635.

It is an arithmetic number, because the mean of its divisors is an integer number (287029878408).

Almost surely, 2^{21256016124645} is an apocalyptic number.

It is an amenable number.

21256016124645 is a deficient number, since it is larger than the sum of its proper divisors (20076286366107).

21256016124645 is a wasteful number, since it uses less digits than its factorization.

21256016124645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 856332 (or 856312 counting only the distinct ones).

The product of its (nonzero) digits is 691200, while the sum is 45.

Adding to 21256016124645 its reverse (54642161065212), we get a palindrome (75898177189857).

The spelling of 21256016124645 in words is "twenty-one trillion, two hundred fifty-six billion, sixteen million, one hundred twenty-four thousand, six hundred forty-five".