21515613984 has 480 divisors, whose sum is σ = 72888076800. Its totient is φ = 6180986880.

The previous prime is 21515613983. The next prime is 21515614009. The reversal of 21515613984 is 48931651512.

It is a happy number.

21515613984 is a `hidden beast` number, since 2 + 1 + 5 + 1 + 561 + 3 + 9 + 84 = 666.

It is not an unprimeable number, because it can be changed into a prime (21515613983) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 25953282 + ... + 25954110.

It is an arithmetic number, because the mean of its divisors is an integer number (151850160).

Almost surely, 2^21515613984 is an apocalyptic number.

21515613984 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 21515613984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36444038400).

21515613984 is an abundant number, since it is smaller than the sum of its proper divisors (51372462816).

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

21515613984 is a wasteful number, since it uses less digits than its factorization.

21515613984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 918 (or 901 counting only the distinct ones).

The product of its digits is 259200, while the sum is 45.

The spelling of 21515613984 in words is "twenty-one billion, five hundred fifteen million, six hundred thirteen thousand, nine hundred eighty-four".