21661635412 has 12 divisors (see below), whose sum is σ = 37977167200. Its totient is φ = 10811016216.

The previous prime is 21661635377. The next prime is 21661635421. The reversal of 21661635412 is 21453616612.

It is a congruent number.

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, 4947912 + ... + 4952287.

Almost surely, 2^21661635412 is an apocalyptic number.

It is an amenable number.

21661635412 is a deficient number, since it is larger than the sum of its proper divisors (16315531788).

21661635412 is a wasteful number, since it uses less digits than its factorization.

21661635412 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9900750 (or 9900748 counting only the distinct ones).

The product of its digits is 51840, while the sum is 37.

The spelling of 21661635412 in words is "twenty-one billion, six hundred sixty-one million, six hundred thirty-five thousand, four hundred twelve".