21506269 has 2 divisors, whose sum is σ = 21506270. Its totient is φ = 21506268.

The previous prime is 21506257. The next prime is 21506279. The reversal of 21506269 is 96260512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16040025 + 5466244 = 4005^2 + 2338^2 .

It is a cyclic number.

It is not a de Polignac number, because 21506269 - 2²³ = 13117661 is a prime.

It is a super-2 number, since 2×21506269² = 925039212600722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21506269.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21506209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10753134 + 10753135.

It is an arithmetic number, because the mean of its divisors is an integer number (10753135).

Almost surely, 2^21506269 is an apocalyptic number.

It is an amenable number.

21506269 is a deficient number, since it is larger than the sum of its proper divisors (1).

21506269 is an equidigital number, since it uses as much as digits as its factorization.

21506269 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6480, while the sum is 31.

The square root of 21506269 is about 4637.4852021327. The cubic root of 21506269 is about 278.0919118824.

The spelling of 21506269 in words is "twenty-one million, five hundred six thousand, two hundred sixty-nine".