21239191 has 2 divisors, whose sum is σ = 21239192. Its totient is φ = 21239190.

The previous prime is 21239177. The next prime is 21239203. The reversal of 21239191 is 19193212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21239191 - 2¹¹ = 21237143 is a prime.

It is a super-2 number, since 2×21239191² = 902206468668962, which contains 22 as substring.

It is equal to p_1344079 and since 21239191 and 1344079 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21249191) 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 as a sum of consecutive naturals, namely, 10619595 + 10619596.

It is an arithmetic number, because the mean of its divisors is an integer number (10619596).

Almost surely, 2^21239191 is an apocalyptic number.

21239191 is a deficient number, since it is larger than the sum of its proper divisors (1).

21239191 is an equidigital number, since it uses as much as digits as its factorization.

21239191 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21239191 is about 4608.5996788612. The cubic root of 21239191 is about 276.9359416052.

The spelling of 21239191 in words is "twenty-one million, two hundred thirty-nine thousand, one hundred ninety-one".