21156249 has 4 divisors (see below), whose sum is σ = 28208336. Its totient is φ = 14104164.

The previous prime is 21156241. The next prime is 21156257. The reversal of 21156249 is 94265112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (21156241) and next prime (21156257).

It is not a de Polignac number, because 21156249 - 2³ = 21156241 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21156241) 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 3 ways as a sum of consecutive naturals, for example, 3526039 + ... + 3526044.

It is an arithmetic number, because the mean of its divisors is an integer number (7052084).

Almost surely, 2^21156249 is an apocalyptic number.

It is an amenable number.

21156249 is a deficient number, since it is larger than the sum of its proper divisors (7052087).

21156249 is an equidigital number, since it uses as much as digits as its factorization.

21156249 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7052086.

The product of its digits is 4320, while the sum is 30.

The square root of 21156249 is about 4599.5922645382. The cubic root of 21156249 is about 276.5749801831.

The spelling of 21156249 in words is "twenty-one million, one hundred fifty-six thousand, two hundred forty-nine".