21087664620 has 288 divisors, whose sum is σ = 69870403008. Its totient is φ = 4730880000.

The previous prime is 21087664607. The next prime is 21087664639. The reversal of 21087664620 is 2646678012.

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 7527220 + ... + 7530020.

It is an arithmetic number, because the mean of its divisors is an integer number (242605566).

Almost surely, 2^21087664620 is an apocalyptic number.

21087664620 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 21087664620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34935201504).

21087664620 is an abundant number, since it is smaller than the sum of its proper divisors (48782738388).

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

21087664620 is a wasteful number, since it uses less digits than its factorization.

21087664620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2913 (or 2900 counting only the distinct ones).

The product of its (nonzero) digits is 193536, while the sum is 42.

The spelling of 21087664620 in words is "twenty-one billion, eighty-seven million, six hundred sixty-four thousand, six hundred twenty".