21252437 has 4 divisors (see below), whose sum is σ = 22176480. Its totient is φ = 20328396.

The previous prime is 21252433. The next prime is 21252443. The reversal of 21252437 is 73425212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21252437 - 2² = 21252433 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21252433) 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, 461987 + ... + 462032.

It is an arithmetic number, because the mean of its divisors is an integer number (5544120).

Almost surely, 2^21252437 is an apocalyptic number.

It is an amenable number.

21252437 is a deficient number, since it is larger than the sum of its proper divisors (924043).

21252437 is an equidigital number, since it uses as much as digits as its factorization.

21252437 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 924042.

The product of its digits is 3360, while the sum is 26.

The square root of 21252437 is about 4610.0365508312. The cubic root of 21252437 is about 276.9935007837.

Adding to 21252437 its reverse (73425212), we get a palindrome (94677649).

The spelling of 21252437 in words is "twenty-one million, two hundred fifty-two thousand, four hundred thirty-seven".