21339251 has 4 divisors (see below), whose sum is σ = 21390600. Its totient is φ = 21287904.

The previous prime is 21339247. The next prime is 21339277. The reversal of 21339251 is 15293312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21339251 - 2² = 21339247 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21339251.

It is not an unprimeable number, because it can be changed into a prime (21339221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25046 + ... + 25883.

It is an arithmetic number, because the mean of its divisors is an integer number (5347650).

Almost surely, 2^21339251 is an apocalyptic number.

21339251 is a deficient number, since it is larger than the sum of its proper divisors (51349).

21339251 is an equidigital number, since it uses as much as digits as its factorization.

21339251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51348.

The product of its digits is 1620, while the sum is 26.

The square root of 21339251 is about 4619.4427153067. The cubic root of 21339251 is about 277.3701516251.

The spelling of 21339251 in words is "twenty-one million, three hundred thirty-nine thousand, two hundred fifty-one".