21553239 has 8 divisors (see below), whose sum is σ = 30250240. Its totient is φ = 13612536.

The previous prime is 21553223. The next prime is 21553243. The reversal of 21553239 is 93235512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21553239 - 2⁴ = 21553223 is a prime.

It is a super-2 number, since 2×21553239² = 929084222782242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21553039) 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 7 ways as a sum of consecutive naturals, for example, 189007 + ... + 189120.

It is an arithmetic number, because the mean of its divisors is an integer number (3781280).

Almost surely, 2^21553239 is an apocalyptic number.

21553239 is a deficient number, since it is larger than the sum of its proper divisors (8697001).

21553239 is a wasteful number, since it uses less digits than its factorization.

21553239 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 378149.

The product of its digits is 8100, while the sum is 30.

The square root of 21553239 is about 4642.5466071974. The cubic root of 21553239 is about 278.2942169164.

The spelling of 21553239 in words is "twenty-one million, five hundred fifty-three thousand, two hundred thirty-nine".