21661013872 has 10 divisors (see below), whose sum is σ = 41968214408. Its totient is φ = 10830506928.

The previous prime is 21661013867. The next prime is 21661013977. The reversal of 21661013872 is 27831016612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 676906668 + ... + 676906699.

Almost surely, 2^21661013872 is an apocalyptic number.

It is an amenable number.

21661013872 is a deficient number, since it is larger than the sum of its proper divisors (20307200536).

21661013872 is a wasteful number, since it uses less digits than its factorization.

21661013872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1353813375 (or 1353813369 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 37.

The spelling of 21661013872 in words is "twenty-one billion, six hundred sixty-one million, thirteen thousand, eight hundred seventy-two".