21373717 has 2 divisors, whose sum is σ = 21373718. Its totient is φ = 21373716.

The previous prime is 21373711. The next prime is 21373771. The reversal of 21373717 is 71737312.

Together with next prime (21373771) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11350161 + 10023556 = 3369^2 + 3166^2 .

It is a cyclic number.

It is not a de Polignac number, because 21373717 - 2⁷ = 21373589 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21373711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10686858 + 10686859.

It is an arithmetic number, because the mean of its divisors is an integer number (10686859).

Almost surely, 2^21373717 is an apocalyptic number.

It is an amenable number.

21373717 is a deficient number, since it is larger than the sum of its proper divisors (1).

21373717 is an equidigital number, since it uses as much as digits as its factorization.

21373717 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6174, while the sum is 31.

The square root of 21373717 is about 4623.1717467557. The cubic root of 21373717 is about 277.5194023714.

The spelling of 21373717 in words is "twenty-one million, three hundred seventy-three thousand, seven hundred seventeen".