20615864 has 8 divisors (see below), whose sum is σ = 38654760. Its totient is φ = 10307928.

The previous prime is 20615851. The next prime is 20615867. The reversal of 20615864 is 46851602.

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

It is a self number, because there is not a number n which added to its sum of digits gives 20615864.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20615867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1288484 + ... + 1288499.

It is an arithmetic number, because the mean of its divisors is an integer number (4831845).

Almost surely, 2^20615864 is an apocalyptic number.

It is an amenable number.

20615864 is a deficient number, since it is larger than the sum of its proper divisors (18038896).

20615864 is a wasteful number, since it uses less digits than its factorization.

20615864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2576989 (or 2576985 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 32.

The square root of 20615864 is about 4540.4695792396. The cubic root of 20615864 is about 274.1998293645.

The spelling of 20615864 in words is "twenty million, six hundred fifteen thousand, eight hundred sixty-four".