21591907 has 2 divisors, whose sum is σ = 21591908. Its totient is φ = 21591906.

The previous prime is 21591893. The next prime is 21591929. The reversal of 21591907 is 70919512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21591907 - 2¹¹ = 21589859 is a prime.

It is not a weakly prime, because it can be changed into another prime (21591007) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10795953 + 10795954.

It is an arithmetic number, because the mean of its divisors is an integer number (10795954).

Almost surely, 2^21591907 is an apocalyptic number.

21591907 is a deficient number, since it is larger than the sum of its proper divisors (1).

21591907 is an equidigital number, since it uses as much as digits as its factorization.

21591907 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5670, while the sum is 34.

The square root of 21591907 is about 4646.7092657062. The cubic root of 21591907 is about 278.4605438400.

The spelling of 21591907 in words is "twenty-one million, five hundred ninety-one thousand, nine hundred seven".