21505499 has 2 divisors, whose sum is σ = 21505500. Its totient is φ = 21505498.

The previous prime is 21505481. The next prime is 21505507. The reversal of 21505499 is 99450512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21505499 - 2⁸ = 21505243 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is equal to p_1359926 and since 21505499 and 1359926 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21505469) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10752749 + 10752750.

It is an arithmetic number, because the mean of its divisors is an integer number (10752750).

Almost surely, 2^21505499 is an apocalyptic number.

21505499 is a deficient number, since it is larger than the sum of its proper divisors (1).

21505499 is an equidigital number, since it uses as much as digits as its factorization.

21505499 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16200, while the sum is 35.

The square root of 21505499 is about 4637.4021822568. The cubic root of 21505499 is about 278.0885929536.

The spelling of 21505499 in words is "twenty-one million, five hundred five thousand, four hundred ninety-nine".