21903449 has 2 divisors, whose sum is σ = 21903450. Its totient is φ = 21903448.

The previous prime is 21903443. The next prime is 21903487. The reversal of 21903449 is 94430912.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12250000 + 9653449 = 3500^2 + 3107^2 .

It is a cyclic number.

It is not a de Polignac number, because 21903449 - 2⁴ = 21903433 is a prime.

It is a super-2 number, since 2×21903449² = 959522156191202, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21903443) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10951724 + 10951725.

It is an arithmetic number, because the mean of its divisors is an integer number (10951725).

Almost surely, 2^21903449 is an apocalyptic number.

It is an amenable number.

21903449 is a deficient number, since it is larger than the sum of its proper divisors (1).

21903449 is an equidigital number, since it uses as much as digits as its factorization.

21903449 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7776, while the sum is 32.

The square root of 21903449 is about 4680.1120713077. The cubic root of 21903449 is about 279.7934233109.

The spelling of 21903449 in words is "twenty-one million, nine hundred three thousand, four hundred forty-nine".