21241391 has 2 divisors, whose sum is σ = 21241392. Its totient is φ = 21241390.

The previous prime is 21241379. The next prime is 21241399. The reversal of 21241391 is 19314212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21241391 - 2⁶ = 21241327 is a prime.

It is a super-2 number, since 2×21241391² = 902393383229762, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21241399) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10620695 + 10620696.

It is an arithmetic number, because the mean of its divisors is an integer number (10620696).

Almost surely, 2^21241391 is an apocalyptic number.

21241391 is a deficient number, since it is larger than the sum of its proper divisors (1).

21241391 is an equidigital number, since it uses as much as digits as its factorization.

21241391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 432, while the sum is 23.

The square root of 21241391 is about 4608.8383568965. The cubic root of 21241391 is about 276.9455031438.

The spelling of 21241391 in words is "twenty-one million, two hundred forty-one thousand, three hundred ninety-one".