21690782920 has 16 divisors (see below), whose sum is σ = 48804261660. Its totient is φ = 8676313152.

The previous prime is 21690782857. The next prime is 21690782941. The reversal of 21690782920 is 2928709612.

It can be written as a sum of positive squares in 2 ways, for example, as 18976164516 + 2714618404 = 137754^2 + 52102^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 271134747 + ... + 271134826.

Almost surely, 2^21690782920 is an apocalyptic number.

21690782920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21690782920 is an abundant number, since it is smaller than the sum of its proper divisors (27113478740).

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

21690782920 is a wasteful number, since it uses less digits than its factorization.

21690782920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 542269584 (or 542269580 counting only the distinct ones).

The product of its (nonzero) digits is 217728, while the sum is 46.

The spelling of 21690782920 in words is "twenty-one billion, six hundred ninety million, seven hundred eighty-two thousand, nine hundred twenty".