21386791 has 2 divisors, whose sum is σ = 21386792. Its totient is φ = 21386790.

The previous prime is 21386773. The next prime is 21386797. The reversal of 21386791 is 19768312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21386791 - 2⁵ = 21386759 is a prime.

It is a super-3 number, since 3×21386791³ (a number of 23 digits) contains 333 as substring.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21386791.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21386797) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10693395 + 10693396.

It is an arithmetic number, because the mean of its divisors is an integer number (10693396).

Almost surely, 2^21386791 is an apocalyptic number.

21386791 is a deficient number, since it is larger than the sum of its proper divisors (1).

21386791 is an equidigital number, since it uses as much as digits as its factorization.

21386791 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18144, while the sum is 37.

The square root of 21386791 is about 4624.5854949390. The cubic root of 21386791 is about 277.5759757341.

The spelling of 21386791 in words is "twenty-one million, three hundred eighty-six thousand, seven hundred ninety-one".