21657420668 has 12 divisors (see below), whose sum is σ = 40815908280. Its totient is φ = 9995732592.

The previous prime is 21657420613. The next prime is 21657420671. The reversal of 21657420668 is 86602475612.

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, 208244378 + ... + 208244481.

It is an arithmetic number, because the mean of its divisors is an integer number (3401325690).

Almost surely, 2^21657420668 is an apocalyptic number.

It is an amenable number.

21657420668 is a deficient number, since it is larger than the sum of its proper divisors (19158487612).

21657420668 is a wasteful number, since it uses less digits than its factorization.

21657420668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 416488876 (or 416488874 counting only the distinct ones).

The product of its (nonzero) digits is 967680, while the sum is 47.

The spelling of 21657420668 in words is "twenty-one billion, six hundred fifty-seven million, four hundred twenty thousand, six hundred sixty-eight".