21372243 has 4 divisors (see below), whose sum is σ = 28496328. Its totient is φ = 14248160.

The previous prime is 21372233. The next prime is 21372269. The reversal of 21372243 is 34227312.

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 21372243 - 2⁴ = 21372227 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21372233) 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, 3562038 + ... + 3562043.

It is an arithmetic number, because the mean of its divisors is an integer number (7124082).

Almost surely, 2^21372243 is an apocalyptic number.

21372243 is a deficient number, since it is larger than the sum of its proper divisors (7124085).

21372243 is an equidigital number, since it uses as much as digits as its factorization.

21372243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7124084.

The product of its digits is 2016, while the sum is 24.

The square root of 21372243 is about 4623.0123296396. The cubic root of 21372243 is about 277.5130226824.

Adding to 21372243 its reverse (34227312), we get a palindrome (55599555).

The spelling of 21372243 in words is "twenty-one million, three hundred seventy-two thousand, two hundred forty-three".