21252651644 has 24 divisors (see below), whose sum is σ = 42511068768. Its totient is φ = 9107043840.

The previous prime is 21252651599. The next prime is 21252651649. The reversal of 21252651644 is 44615625212.

It is a junction number, because it is equal to n+sod(n) for n = 21252651598 and 21252651607.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21252651649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 176324 + ... + 271284.

It is an arithmetic number, because the mean of its divisors is an integer number (1771294532).

Almost surely, 2^21252651644 is an apocalyptic number.

It is an amenable number.

21252651644 is an abundant number, since it is smaller than the sum of its proper divisors (21258417124).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21252651644 is a wasteful number, since it uses less digits than its factorization.

21252651644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 102965 (or 102963 counting only the distinct ones).

The product of its digits is 115200, while the sum is 38.

The spelling of 21252651644 in words is "twenty-one billion, two hundred fifty-two million, six hundred fifty-one thousand, six hundred forty-four".