21909249 has 6 divisors (see below), whose sum is σ = 31646706. Its totient is φ = 14606160.

The previous prime is 21909247. The next prime is 21909253. The reversal of 21909249 is 94290912.

It can be written as a sum of positive squares in only one way, i.e., 21790224 + 119025 = 4668^2 + 345^2 .

It is not a de Polignac number, because 21909249 - 2¹ = 21909247 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21909247) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1217172 + ... + 1217189.

It is an arithmetic number, because the mean of its divisors is an integer number (5274451).

Almost surely, 2^21909249 is an apocalyptic number.

It is an amenable number.

21909249 is a deficient number, since it is larger than the sum of its proper divisors (9737457).

21909249 is a wasteful number, since it uses less digits than its factorization.

21909249 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2434367 (or 2434364 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 36.

The square root of 21909249 is about 4680.7316735741. The cubic root of 21909249 is about 279.8181174224.

The spelling of 21909249 in words is "twenty-one million, nine hundred nine thousand, two hundred forty-nine".