21499649 has 2 divisors, whose sum is σ = 21499650. Its totient is φ = 21499648.

The previous prime is 21499631. The next prime is 21499663. The reversal of 21499649 is 94699412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14440000 + 7059649 = 3800^2 + 2657^2 .

It is a cyclic number.

It is not a de Polignac number, because 21499649 - 2²⁰ = 20451073 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21499619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10749824 + 10749825.

It is an arithmetic number, because the mean of its divisors is an integer number (10749825).

Almost surely, 2^21499649 is an apocalyptic number.

It is an amenable number.

21499649 is a deficient number, since it is larger than the sum of its proper divisors (1).

21499649 is an equidigital number, since it uses as much as digits as its factorization.

21499649 is an evil number, because the sum of its binary digits is even.

The product of its digits is 139968, while the sum is 44.

The square root of 21499649 is about 4636.7713982900. The cubic root of 21499649 is about 278.0633751275.

The spelling of 21499649 in words is "twenty-one million, four hundred ninety-nine thousand, six hundred forty-nine".