21107791 has 2 divisors, whose sum is σ = 21107792. Its totient is φ = 21107790.

The previous prime is 21107789. The next prime is 21107839. The reversal of 21107791 is 19770112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21107791 - 2¹ = 21107789 is a prime.

Together with 21107789, it forms a pair of twin primes.

It is equal to p_1336357 and since 21107791 and 1336357 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 (21107701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10553895 + 10553896.

It is an arithmetic number, because the mean of its divisors is an integer number (10553896).

Almost surely, 2^21107791 is an apocalyptic number.

21107791 is a deficient number, since it is larger than the sum of its proper divisors (1).

21107791 is an equidigital number, since it uses as much as digits as its factorization.

21107791 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 882, while the sum is 28.

The square root of 21107791 is about 4594.3216038932. The cubic root of 21107791 is about 276.3636554506.

The spelling of 21107791 in words is "twenty-one million, one hundred seven thousand, seven hundred ninety-one".