21809973124 has 27 divisors (see below), whose sum is σ = 39142805583. Its totient is φ = 10633104000.

The previous prime is 21809973071. The next prime is 21809973193. The reversal of 21809973124 is 42137990812.

It is a happy number.

The square root of 21809973124 is 147682.

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

It can be written as a sum of positive squares in 4 ways, for example, as 15059707524 + 6750265600 = 122718^2 + 82160^2 .

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, 12109024 + ... + 12110824.

Almost surely, 2^21809973124 is an apocalyptic number.

21809973124 is the 147682-nd square number.

It is an amenable number.

21809973124 is a deficient number, since it is larger than the sum of its proper divisors (17332832459).

21809973124 is an frugal number, since it uses more digits than its factorization.

21809973124 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3688 (or 1844 counting only the distinct ones).

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

The spelling of 21809973124 in words is "twenty-one billion, eight hundred nine million, nine hundred seventy-three thousand, one hundred twenty-four".