21615027264 has 252 divisors, whose sum is σ = 67813920252. Its totient is φ = 6559580160.

The previous prime is 21615027263. The next prime is 21615027277. The reversal of 21615027264 is 46272051612.

It is a happy number.

21615027264 is a `hidden beast` number, since 21 + 6 + 1 + 502 + 72 + 64 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 13644108864 + 7970918400 = 116808^2 + 89280^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21615027263) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 9408964 + ... + 9411260.

Almost surely, 2^21615027264 is an apocalyptic number.

21615027264 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 21615027264, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33906960126).

21615027264 is an abundant number, since it is smaller than the sum of its proper divisors (46198892988).

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

21615027264 is a wasteful number, since it uses less digits than its factorization.

21615027264 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2394 (or 2350 counting only the distinct ones).

The product of its (nonzero) digits is 40320, while the sum is 36.

Adding to 21615027264 its reverse (46272051612), we get a palindrome (67887078876).

The spelling of 21615027264 in words is "twenty-one billion, six hundred fifteen million, twenty-seven thousand, two hundred sixty-four".