21595391 has 2 divisors, whose sum is σ = 21595392. Its totient is φ = 21595390.

The previous prime is 21595369. The next prime is 21595393. The reversal of 21595391 is 19359512.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21595391 is a prime.

Together with 21595393, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21595393) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10797695 + 10797696.

It is an arithmetic number, because the mean of its divisors is an integer number (10797696).

Almost surely, 2^21595391 is an apocalyptic number.

21595391 is a deficient number, since it is larger than the sum of its proper divisors (1).

21595391 is an equidigital number, since it uses as much as digits as its factorization.

21595391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12150, while the sum is 35.

The square root of 21595391 is about 4647.0841395438. The cubic root of 21595391 is about 278.4755201976.

The spelling of 21595391 in words is "twenty-one million, five hundred ninety-five thousand, three hundred ninety-one".