21023515440 has 320 divisors, whose sum is σ = 74756822400. Its totient is φ = 5426528256.

The previous prime is 21023515399. The next prime is 21023515463. The reversal of 21023515440 is 4451532012.

21023515440 is a `hidden beast` number, since 2 + 102 + 3 + 515 + 4 + 40 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 18620796 + ... + 18621924.

It is an arithmetic number, because the mean of its divisors is an integer number (233615070).

Almost surely, 2^21023515440 is an apocalyptic number.

21023515440 is a gapful number since it is divisible by the number (20) 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 21023515440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37378411200).

21023515440 is an abundant number, since it is smaller than the sum of its proper divisors (53733306960).

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

21023515440 is a wasteful number, since it uses less digits than its factorization.

21023515440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1421 (or 1409 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 27.

The spelling of 21023515440 in words is "twenty-one billion, twenty-three million, five hundred fifteen thousand, four hundred forty".