20661656 has 8 divisors (see below), whose sum is σ = 38740620. Its totient is φ = 10330824.

The previous prime is 20661643. The next prime is 20661689. The reversal of 20661656 is 65616602.

It is a tau number, because it is divible by the number of its divisors (8).

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, 1291346 + ... + 1291361.

Almost surely, 2^20661656 is an apocalyptic number.

It is an amenable number.

20661656 is a deficient number, since it is larger than the sum of its proper divisors (18078964).

20661656 is a wasteful number, since it uses less digits than its factorization.

20661656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2582713 (or 2582709 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 32.

The square root of 20661656 is about 4545.5094323959. The cubic root of 20661656 is about 274.4026969790.

The spelling of 20661656 in words is "twenty million, six hundred sixty-one thousand, six hundred fifty-six".