21208813556 has 48 divisors (see below), whose sum is σ = 46361613312. Its totient is φ = 8278848000.

The previous prime is 21208813541. The next prime is 21208813601. The reversal of 21208813556 is 65531880212.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 703895 + ... + 733406.

It is an arithmetic number, because the mean of its divisors is an integer number (965866944).

Almost surely, 2^21208813556 is an apocalyptic number.

It is an amenable number.

21208813556 is an abundant number, since it is smaller than the sum of its proper divisors (25152799756).

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

21208813556 is a wasteful number, since it uses less digits than its factorization.

21208813556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1437360 (or 1437358 counting only the distinct ones).

The product of its (nonzero) digits is 115200, while the sum is 41.

The spelling of 21208813556 in words is "twenty-one billion, two hundred eight million, eight hundred thirteen thousand, five hundred fifty-six".