21261249 has 12 divisors (see below), whose sum is σ = 31364736. Its totient is φ = 13872312.

The previous prime is 21261241. The next prime is 21261259. The reversal of 21261249 is 94216212.

21261249 is a `hidden beast` number, since 2 + 1 + 2 + 612 + 49 = 666.

It is not a de Polignac number, because 21261249 - 2³ = 21261241 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21261241) 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 11 ways as a sum of consecutive naturals, for example, 24709 + ... + 25554.

It is an arithmetic number, because the mean of its divisors is an integer number (2613728).

Almost surely, 2^21261249 is an apocalyptic number.

It is an amenable number.

21261249 is a deficient number, since it is larger than the sum of its proper divisors (10103487).

21261249 is a wasteful number, since it uses less digits than its factorization.

21261249 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50316 (or 50313 counting only the distinct ones).

The product of its digits is 1728, while the sum is 27.

The square root of 21261249 is about 4610.9921925763. The cubic root of 21261249 is about 277.0317792088.

It can be divided in two parts, 2126 and 1249, that added together give a cube (3375 = 15³).

The spelling of 21261249 in words is "twenty-one million, two hundred sixty-one thousand, two hundred forty-nine".