21500393 has 8 divisors (see below), whose sum is σ = 22886568. Its totient is φ = 20127744.

The previous prime is 21500321. The next prime is 21500429. The reversal of 21500393 is 39300512.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 2166784 + 19333609 = 1472^2 + 4397^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21500393 - 2⁸ = 21500137 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21500593) 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, 5 + ... + 6557.

It is an arithmetic number, because the mean of its divisors is an integer number (2860821).

Almost surely, 2^21500393 is an apocalyptic number.

It is an amenable number.

21500393 is a deficient number, since it is larger than the sum of its proper divisors (1386175).

21500393 is a wasteful number, since it uses less digits than its factorization.

21500393 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6763.

The product of its (nonzero) digits is 810, while the sum is 23.

The square root of 21500393 is about 4636.8516258341. The cubic root of 21500393 is about 278.0665825716.

The spelling of 21500393 in words is "twenty-one million, five hundred thousand, three hundred ninety-three".