20971664 has 40 divisors (see below), whose sum is σ = 47580288. Its totient is φ = 8766720.

The previous prime is 20971661. The next prime is 20971667. The reversal of 20971664 is 46617902.

It is an interprime number because it is at equal distance from previous prime (20971661) and next prime (20971667).

It is not an unprimeable number, because it can be changed into a prime (20971661) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2309 + ... + 6875.

Almost surely, 2^20971664 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20971664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23790144).

20971664 is an abundant number, since it is smaller than the sum of its proper divisors (26608624).

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

20971664 is a wasteful number, since it uses less digits than its factorization.

20971664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4623 (or 4617 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 35.

The square root of 20971664 is about 4579.4829402455. The cubic root of 20971664 is about 275.7682715047.

The spelling of 20971664 in words is "twenty million, nine hundred seventy-one thousand, six hundred sixty-four".