21391363 has 4 divisors (see below), whose sum is σ = 24447280. Its totient is φ = 18335448.

The previous prime is 21391361. The next prime is 21391367. The reversal of 21391363 is 36319312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21391363 - 2¹ = 21391361 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21391361) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1527948 + ... + 1527961.

It is an arithmetic number, because the mean of its divisors is an integer number (6111820).

Almost surely, 2^21391363 is an apocalyptic number.

21391363 is a deficient number, since it is larger than the sum of its proper divisors (3055917).

21391363 is an equidigital number, since it uses as much as digits as its factorization.

21391363 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3055916.

The product of its digits is 2916, while the sum is 28.

The square root of 21391363 is about 4625.0797830956. The cubic root of 21391363 is about 277.5957540938.

The spelling of 21391363 in words is "twenty-one million, three hundred ninety-one thousand, three hundred sixty-three".