21865040 has 20 divisors (see below), whose sum is σ = 50836404. Its totient is φ = 8745984.

The previous prime is 21865037. The next prime is 21865057. The reversal of 21865040 is 4056812.

It can be written as a sum of positive squares in 2 ways, for example, as 7907344 + 13957696 = 2812^2 + 3736^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a hoax number, since the sum of its digits (26) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136577 + ... + 136736.

Almost surely, 2^21865040 is an apocalyptic number.

21865040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21865040 is an abundant number, since it is smaller than the sum of its proper divisors (28971364).

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

21865040 is a wasteful number, since it uses less digits than its factorization.

21865040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 273326 (or 273320 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 26.

The square root of 21865040 is about 4676.0068434509. The cubic root of 21865040 is about 279.6297828219.

The spelling of 21865040 in words is "twenty-one million, eight hundred sixty-five thousand, forty".