21566719 has 2 divisors, whose sum is σ = 21566720. Its totient is φ = 21566718.

The previous prime is 21566681. The next prime is 21566737. The reversal of 21566719 is 91766512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21566719 - 2¹¹ = 21564671 is a prime.

It is a super-2 number, since 2×21566719² = 930246736849922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21566119) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10783359 + 10783360.

It is an arithmetic number, because the mean of its divisors is an integer number (10783360).

Almost surely, 2^21566719 is an apocalyptic number.

21566719 is a deficient number, since it is larger than the sum of its proper divisors (1).

21566719 is an equidigital number, since it uses as much as digits as its factorization.

21566719 is an evil number, because the sum of its binary digits is even.

The product of its digits is 22680, while the sum is 37.

The square root of 21566719 is about 4643.9981696809. The cubic root of 21566719 is about 278.3522224941.

The spelling of 21566719 in words is "twenty-one million, five hundred sixty-six thousand, seven hundred nineteen".