21990708506 has 16 divisors (see below), whose sum is σ = 35728797384. Its totient is φ = 10090887744.

The previous prime is 21990708491. The next prime is 21990708517. The reversal of 21990708506 is 60580709912.

It can be written as a sum of positive squares in 4 ways, for example, as 18209073481 + 3781635025 = 134941^2 + 61495^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2440001 + ... + 2448996.

Almost surely, 2^21990708506 is an apocalyptic number.

21990708506 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21990708506 is a deficient number, since it is larger than the sum of its proper divisors (13738088878).

21990708506 is a wasteful number, since it uses less digits than its factorization.

21990708506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4889185.

The product of its (nonzero) digits is 272160, while the sum is 47.

The spelling of 21990708506 in words is "twenty-one billion, nine hundred ninety million, seven hundred eight thousand, five hundred six".