20691864 has 24 divisors (see below), whose sum is σ = 56040660. Its totient is φ = 6897264.

The previous prime is 20691859. The next prime is 20691887. The reversal of 20691864 is 46819602.

It is a tau number, because it is divible by the number of its divisors (24).

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

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, 143622 + ... + 143765.

Almost surely, 2^20691864 is an apocalyptic number.

20691864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

20691864 is an abundant number, since it is smaller than the sum of its proper divisors (35348796).

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

20691864 is a wasteful number, since it uses less digits than its factorization.

20691864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 287399 (or 287392 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 36.

The square root of 20691864 is about 4548.8310586347. The cubic root of 20691864 is about 274.5363603581.

The spelling of 20691864 in words is "twenty million, six hundred ninety-one thousand, eight hundred sixty-four".