20657664 has 60 divisors (see below), whose sum is σ = 59632716. Its totient is φ = 6884352.

The previous prime is 20657653. The next prime is 20657677. The reversal of 20657664 is 46675602.

20657664 is a `hidden beast` number, since 20 + 6 + 576 + 64 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a zygodrome in base 8.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2367 + ... + 6849.

Almost surely, 2^20657664 is an apocalyptic number.

20657664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20657664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29816358).

20657664 is an abundant number, since it is smaller than the sum of its proper divisors (38975052).

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

20657664 is an equidigital number, since it uses as much as digits as its factorization.

20657664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4507 (or 4488 counting only the distinct ones).

The product of its (nonzero) digits is 60480, while the sum is 36.

The square root of 20657664 is about 4545.0702964861. The cubic root of 20657664 is about 274.3850235630.

It can be divided in two parts, 20657 and 664, that added together give a triangular number (21321 = T₂₀₆).

The spelling of 20657664 in words is "twenty million, six hundred fifty-seven thousand, six hundred sixty-four".