21501644436 has 72 divisors (see below), whose sum is σ = 55049458464. Its totient is φ = 7075627200.

The previous prime is 21501644413. The next prime is 21501644453. The reversal of 21501644436 is 63444610512.

21501644436 is a `hidden beast` number, since 2 + 1 + 5 + 0 + 1 + 644 + 4 + 3 + 6 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21501644436.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1119111 + ... + 1138161.

It is an arithmetic number, because the mean of its divisors is an integer number (764575812).

Almost surely, 2^21501644436 is an apocalyptic number.

It is an amenable number.

21501644436 is an abundant number, since it is smaller than the sum of its proper divisors (33547814028).

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

21501644436 is a wasteful number, since it uses less digits than its factorization.

21501644436 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19461 (or 19456 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 36.

The spelling of 21501644436 in words is "twenty-one billion, five hundred one million, six hundred forty-four thousand, four hundred thirty-six".