21237213 has 4 divisors (see below), whose sum is σ = 28316288. Its totient is φ = 14158140.

The previous prime is 21237197. The next prime is 21237217. The reversal of 21237213 is 31273212.

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 not a de Polignac number, because 21237213 - 2⁴ = 21237197 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21237213.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21237217) 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, 3539533 + ... + 3539538.

It is an arithmetic number, because the mean of its divisors is an integer number (7079072).

Almost surely, 2^21237213 is an apocalyptic number.

It is an amenable number.

21237213 is a deficient number, since it is larger than the sum of its proper divisors (7079075).

21237213 is an equidigital number, since it uses as much as digits as its factorization.

21237213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7079074.

The product of its digits is 504, while the sum is 21.

The square root of 21237213 is about 4608.3850750561. The cubic root of 21237213 is about 276.9273443490.

The spelling of 21237213 in words is "twenty-one million, two hundred thirty-seven thousand, two hundred thirteen".