21087819936 has 144 divisors (see below), whose sum is σ = 64196391168. Its totient is φ = 6802444800.

The previous prime is 21087819919. The next prime is 21087819947. The reversal of 21087819936 is 63991878012.

It is a tau number, because it is divible by the number of its divisors (144).

It is a super-2 number, since 2×21087819936² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 197316 + ... + 284796.

It is an arithmetic number, because the mean of its divisors is an integer number (445808272).

Almost surely, 2^21087819936 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 21087819936, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32098195584).

21087819936 is an abundant number, since it is smaller than the sum of its proper divisors (43108571232).

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

21087819936 is an equidigital number, since it uses as much as digits as its factorization.

21087819936 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87537 (or 87517 counting only the distinct ones).

The product of its (nonzero) digits is 1306368, while the sum is 54.

The spelling of 21087819936 in words is "twenty-one billion, eighty-seven million, eight hundred nineteen thousand, nine hundred thirty-six".