21387892516 has 27 divisors (see below), whose sum is σ = 37928245873. Its totient is φ = 10553111360.

The previous prime is 21387892501. The next prime is 21387892531. The reversal of 21387892516 is 61529878312.

It is a happy number.

The square root of 21387892516 is 146246.

It is a perfect power (a square), and thus also a powerful number.

It is an interprime number because it is at equal distance from previous prime (21387892501) and next prime (21387892531).

It can be written as a sum of positive squares in only one way, i.e., 3752052516 + 17635840000 = 61254^2 + 132800^2 .

It is a super-4 number, since 4×21387892516⁴ (a number of 42 digits) contains 4444 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 24276396 + ... + 24277276.

Almost surely, 2^21387892516 is an apocalyptic number.

21387892516 is the 146246-th square number.

It is an amenable number.

21387892516 is a deficient number, since it is larger than the sum of its proper divisors (16540353357).

21387892516 is an frugal number, since it uses more digits than its factorization.

21387892516 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1932 (or 966 counting only the distinct ones).

The product of its digits is 1451520, while the sum is 52.

The spelling of 21387892516 in words is "twenty-one billion, three hundred eighty-seven million, eight hundred ninety-two thousand, five hundred sixteen".