21252609 has 12 divisors (see below), whose sum is σ = 35083776. Its totient is φ = 12144312.

The previous prime is 21252607. The next prime is 21252611. The reversal of 21252609 is 90625212.

21252609 is a `hidden beast` number, since 2 + 1 + 2 + 52 + 609 = 666.

It is an interprime number because it is at equal distance from previous prime (21252607) and next prime (21252611).

It is not a de Polignac number, because 21252609 - 2¹ = 21252607 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21252607) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 168609 + ... + 168734.

It is an arithmetic number, because the mean of its divisors is an integer number (2923648).

Almost surely, 2^21252609 is an apocalyptic number.

It is an amenable number.

21252609 is a deficient number, since it is larger than the sum of its proper divisors (13831167).

21252609 is a wasteful number, since it uses less digits than its factorization.

21252609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 337356 (or 337353 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 21252609 is about 4610.0552057432. The cubic root of 21252609 is about 276.9942480353.

The spelling of 21252609 in words is "twenty-one million, two hundred fifty-two thousand, six hundred nine".