21660791 has 2 divisors, whose sum is σ = 21660792. Its totient is φ = 21660790.

The previous prime is 21660761. The next prime is 21660827. The reversal of 21660791 is 19706612.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21660791 - 2¹⁴ = 21644407 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21660701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830395 + 10830396.

It is an arithmetic number, because the mean of its divisors is an integer number (10830396).

Almost surely, 2^21660791 is an apocalyptic number.

21660791 is a deficient number, since it is larger than the sum of its proper divisors (1).

21660791 is an equidigital number, since it uses as much as digits as its factorization.

21660791 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4536, while the sum is 32.

The square root of 21660791 is about 4654.1154906169. The cubic root of 21660791 is about 278.7563508778.

The spelling of 21660791 in words is "twenty-one million, six hundred sixty thousand, seven hundred ninety-one".