21662791 has 2 divisors, whose sum is σ = 21662792. Its totient is φ = 21662790.

The previous prime is 21662789. The next prime is 21662813. The reversal of 21662791 is 19726612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21662791 - 2¹ = 21662789 is a prime.

Together with 21662789, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21662731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10831395 + 10831396.

It is an arithmetic number, because the mean of its divisors is an integer number (10831396).

Almost surely, 2^21662791 is an apocalyptic number.

21662791 is a deficient number, since it is larger than the sum of its proper divisors (1).

21662791 is an equidigital number, since it uses as much as digits as its factorization.

21662791 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9072, while the sum is 34.

The square root of 21662791 is about 4654.3303492554. The cubic root of 21662791 is about 278.7649300589.

The spelling of 21662791 in words is "twenty-one million, six hundred sixty-two thousand, seven hundred ninety-one".