21769717 has 2 divisors, whose sum is σ = 21769718. Its totient is φ = 21769716.

The previous prime is 21769681. The next prime is 21769733. The reversal of 21769717 is 71796712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20921476 + 848241 = 4574^2 + 921^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21769717 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21769717.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21769747) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10884858 + 10884859.

It is an arithmetic number, because the mean of its divisors is an integer number (10884859).

Almost surely, 2^21769717 is an apocalyptic number.

It is an amenable number.

21769717 is a deficient number, since it is larger than the sum of its proper divisors (1).

21769717 is an equidigital number, since it uses as much as digits as its factorization.

21769717 is an evil number, because the sum of its binary digits is even.

The product of its digits is 37044, while the sum is 40.

The square root of 21769717 is about 4665.8029319722. The cubic root of 21769717 is about 279.2228321339. Note that the first 3 decimals are identical.

The spelling of 21769717 in words is "twenty-one million, seven hundred sixty-nine thousand, seven hundred seventeen".