21387630820 has 72 divisors (see below), whose sum is σ = 47555605440. Its totient is φ = 8057456640.

The previous prime is 21387630799. The next prime is 21387630841. The reversal of 21387630820 is 2803678312.

It is an interprime number because it is at equal distance from previous prime (21387630799) and next prime (21387630841).

It is a super-2 number, since 2×21387630820² (a number of 21 digits) contains 22 as substring.

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 23 ways as a sum of consecutive naturals, for example, 14153865 + ... + 14155375.

It is an arithmetic number, because the mean of its divisors is an integer number (660494520).

Almost surely, 2^21387630820 is an apocalyptic number.

21387630820 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 21387630820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23777802720).

21387630820 is an abundant number, since it is smaller than the sum of its proper divisors (26167974620).

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

21387630820 is a wasteful number, since it uses less digits than its factorization.

21387630820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1925 (or 1730 counting only the distinct ones).

The product of its (nonzero) digits is 96768, while the sum is 40.

The spelling of 21387630820 in words is "twenty-one billion, three hundred eighty-seven million, six hundred thirty thousand, eight hundred twenty".