21191239 has 2 divisors, whose sum is σ = 21191240. Its totient is φ = 21191238.

The previous prime is 21191201. The next prime is 21191263. The reversal of 21191239 is 93219112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21191239 - 2⁷ = 21191111 is a prime.

It is a super-2 number, since 2×21191239² = 898137220710242, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21191279) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10595619 + 10595620.

It is an arithmetic number, because the mean of its divisors is an integer number (10595620).

Almost surely, 2^21191239 is an apocalyptic number.

21191239 is a deficient number, since it is larger than the sum of its proper divisors (1).

21191239 is an equidigital number, since it uses as much as digits as its factorization.

21191239 is an evil number, because the sum of its binary digits is even.

The product of its digits is 972, while the sum is 28.

The square root of 21191239 is about 4603.3942911725. The cubic root of 21191239 is about 276.7273705930.

The spelling of 21191239 in words is "twenty-one million, one hundred ninety-one thousand, two hundred thirty-nine".