21504051604 has 96 divisors (see below), whose sum is σ = 47967897600. Its totient is φ = 8393817600.

The previous prime is 21504051581. The next prime is 21504051637. The reversal of 21504051604 is 40615040512.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 708174 + ... + 737914.

It is an arithmetic number, because the mean of its divisors is an integer number (499665600).

Almost surely, 2^21504051604 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21504051604, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23983948800).

21504051604 is an abundant number, since it is smaller than the sum of its proper divisors (26463845996).

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

21504051604 is a wasteful number, since it uses less digits than its factorization.

21504051604 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29814 (or 29798 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 28.

The spelling of 21504051604 in words is "twenty-one billion, five hundred four million, fifty-one thousand, six hundred four".