21695669 has 2 divisors, whose sum is σ = 21695670. Its totient is φ = 21695668.

The previous prime is 21695627. The next prime is 21695747. The reversal of 21695669 is 96659612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20133169 + 1562500 = 4487^2 + 1250^2 .

It is a cyclic number.

It is not a de Polignac number, because 21695669 - 2²⁰ = 20647093 is a prime.

It is a super-2 number, since 2×21695669² = 941404106715122, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21695269) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10847834 + 10847835.

It is an arithmetic number, because the mean of its divisors is an integer number (10847835).

Almost surely, 2^21695669 is an apocalyptic number.

It is an amenable number.

21695669 is a deficient number, since it is larger than the sum of its proper divisors (1).

21695669 is an equidigital number, since it uses as much as digits as its factorization.

21695669 is an evil number, because the sum of its binary digits is even.

The product of its digits is 174960, while the sum is 44.

The square root of 21695669 is about 4657.8609897677. The cubic root of 21695669 is about 278.9058875888.

The spelling of 21695669 in words is "twenty-one million, six hundred ninety-five thousand, six hundred sixty-nine".