21731249 has 12 divisors (see below), whose sum is σ = 22748544. Its totient is φ = 20748024.

The previous prime is 21731243. The next prime is 21731257. The reversal of 21731249 is 94213712.

It is not a de Polignac number, because 21731249 - 2¹⁶ = 21665713 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 (21731243) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 210932 + ... + 211034.

It is an arithmetic number, because the mean of its divisors is an integer number (1895712).

Almost surely, 2^21731249 is an apocalyptic number.

It is an amenable number.

21731249 is a deficient number, since it is larger than the sum of its proper divisors (1017295).

21731249 is an equidigital number, since it uses as much as digits as its factorization.

21731249 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 284 (or 217 counting only the distinct ones).

The product of its digits is 3024, while the sum is 29.

The square root of 21731249 is about 4661.6787748621. The cubic root of 21731249 is about 279.0582690268.

The spelling of 21731249 in words is "twenty-one million, seven hundred thirty-one thousand, two hundred forty-nine".