21249431 has 8 divisors (see below), whose sum is σ = 25122720. Its totient is φ = 17585568.

The previous prime is 21249331. The next prime is 21249443. The reversal of 21249431 is 13494212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21249431 - 2¹⁸ = 20987287 is a prime.

It is a super-2 number, since 2×21249431² = 903076635647522, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21249431.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21249331) 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 7 ways as a sum of consecutive naturals, for example, 52136 + ... + 52541.

It is an arithmetic number, because the mean of its divisors is an integer number (3140340).

Almost surely, 2^21249431 is an apocalyptic number.

21249431 is a deficient number, since it is larger than the sum of its proper divisors (3873289).

21249431 is a wasteful number, since it uses less digits than its factorization.

21249431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104713.

The product of its digits is 1728, while the sum is 26.

The square root of 21249431 is about 4609.7105115180. The cubic root of 21249431 is about 276.9804406074.

The spelling of 21249431 in words is "twenty-one million, two hundred forty-nine thousand, four hundred thirty-one".