21945249 has 20 divisors (see below), whose sum is σ = 34712964. Its totient is φ = 13768704.

The previous prime is 21945239. The next prime is 21945263. The reversal of 21945249 is 94254912.

It can be written as a sum of positive squares in 2 ways, for example, as 16257024 + 5688225 = 4032^2 + 2385^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21945249 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21945229) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 6592 + ... + 9345.

Almost surely, 2^21945249 is an apocalyptic number.

It is an amenable number.

21945249 is a deficient number, since it is larger than the sum of its proper divisors (12767715).

21945249 is a wasteful number, since it uses less digits than its factorization.

21945249 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15966 (or 15957 counting only the distinct ones).

The product of its digits is 25920, while the sum is 36.

The square root of 21945249 is about 4684.5756478042. The cubic root of 21945249 is about 279.9712938258.

The spelling of 21945249 in words is "twenty-one million, nine hundred forty-five thousand, two hundred forty-nine".