21247275 has 24 divisors (see below), whose sum is σ = 40148224. Its totient is φ = 9712800.

The previous prime is 21247273. The next prime is 21247309. The reversal of 21247275 is 57274212.

It is not a de Polignac number, because 21247275 - 2¹ = 21247273 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21247271) 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 23 ways as a sum of consecutive naturals, for example, 19711 + ... + 20760.

Almost surely, 2^21247275 is an apocalyptic number.

21247275 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21247275 is a deficient number, since it is larger than the sum of its proper divisors (18900949).

21247275 is a wasteful number, since it uses less digits than its factorization.

21247275 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40491 (or 40486 counting only the distinct ones).

The product of its digits is 7840, while the sum is 30.

The square root of 21247275 is about 4609.4766514215. The cubic root of 21247275 is about 276.9710726698.

The spelling of 21247275 in words is "twenty-one million, two hundred forty-seven thousand, two hundred seventy-five".