21237439 has 4 divisors (see below), whose sum is σ = 21331224. Its totient is φ = 21143656.

The previous prime is 21237431. The next prime is 21237493. The reversal of 21237439 is 93473212.

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 21237439 - 2³ = 21237431 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21237439.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21237431) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 46552 + ... + 47005.

It is an arithmetic number, because the mean of its divisors is an integer number (5332806).

Almost surely, 2^21237439 is an apocalyptic number.

21237439 is a deficient number, since it is larger than the sum of its proper divisors (93785).

21237439 is an equidigital number, since it uses as much as digits as its factorization.

21237439 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 93784.

The product of its digits is 9072, while the sum is 31.

The square root of 21237439 is about 4608.4095955112. The cubic root of 21237439 is about 276.9283266712.

The spelling of 21237439 in words is "twenty-one million, two hundred thirty-seven thousand, four hundred thirty-nine".