21561469 has 2 divisors, whose sum is σ = 21561470. Its totient is φ = 21561468.

The previous prime is 21561443. The next prime is 21561479. The reversal of 21561469 is 96416512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14538969 + 7022500 = 3813^2 + 2650^2 .

It is a cyclic number.

It is not a de Polignac number, because 21561469 - 2⁷ = 21561341 is a prime.

It is a super-2 number, since 2×21561469² = 929793890875922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21561479) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10780734 + 10780735.

It is an arithmetic number, because the mean of its divisors is an integer number (10780735).

Almost surely, 2^21561469 is an apocalyptic number.

It is an amenable number.

21561469 is a deficient number, since it is larger than the sum of its proper divisors (1).

21561469 is an equidigital number, since it uses as much as digits as its factorization.

21561469 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12960, while the sum is 34.

The square root of 21561469 is about 4643.4328895764. The cubic root of 21561469 is about 278.3296341754.

The spelling of 21561469 in words is "twenty-one million, five hundred sixty-one thousand, four hundred sixty-nine".