21218583556 has 27 divisors (see below), whose sum is σ = 37437325023. Its totient is φ = 10522911840.

The previous prime is 21218583527. The next prime is 21218583557. The reversal of 21218583556 is 65538581212.

The square root of 21218583556 is 145666.

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 1163492100 + 20055091456 = 34110^2 + 141616^2 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21218583557) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 50400226 + ... + 50400646.

Almost surely, 2^21218583556 is an apocalyptic number.

21218583556 is the 145666-th square number.

It is an amenable number.

21218583556 is a deficient number, since it is larger than the sum of its proper divisors (16218741467).

21218583556 is an frugal number, since it uses more digits than its factorization.

21218583556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1192 (or 596 counting only the distinct ones).

The product of its digits is 576000, while the sum is 46.

The spelling of 21218583556 in words is "twenty-one billion, two hundred eighteen million, five hundred eighty-three thousand, five hundred fifty-six".