21506373504 has 960 divisors, whose sum is σ = 84044083200. Its totient is φ = 5337446400.

The previous prime is 21506373487. The next prime is 21506373509. The reversal of 21506373504 is 40537360512.

21506373504 is a `hidden beast` number, since 2 + 15 + 0 + 637 + 3 + 5 + 0 + 4 = 666.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21506373509) by changing a digit.

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 119 ways as a sum of consecutive naturals, for example, 272232537 + ... + 272232615.

It is an arithmetic number, because the mean of its divisors is an integer number (87545920).

Almost surely, 2^21506373504 is an apocalyptic number.

21506373504 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21506373504, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42022041600).

21506373504 is an abundant number, since it is smaller than the sum of its proper divisors (62537709696).

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

21506373504 is a wasteful number, since it uses less digits than its factorization.

21506373504 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165 (or 133 counting only the distinct ones).

The product of its (nonzero) digits is 75600, while the sum is 36.

The spelling of 21506373504 in words is "twenty-one billion, five hundred six million, three hundred seventy-three thousand, five hundred four".