21539449 has 2 divisors, whose sum is σ = 21539450. Its totient is φ = 21539448.

The previous prime is 21539417. The next prime is 21539467. The reversal of 21539449 is 94493512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11022400 + 10517049 = 3320^2 + 3243^2 .

It is a cyclic number.

It is not a de Polignac number, because 21539449 - 2⁵ = 21539417 is a prime.

It is not a weakly prime, because it can be changed into another prime (21539149) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10769724 + 10769725.

It is an arithmetic number, because the mean of its divisors is an integer number (10769725).

Almost surely, 2^21539449 is an apocalyptic number.

It is an amenable number.

21539449 is a deficient number, since it is larger than the sum of its proper divisors (1).

21539449 is an equidigital number, since it uses as much as digits as its factorization.

21539449 is an evil number, because the sum of its binary digits is even.

The product of its digits is 38880, while the sum is 37.

The square root of 21539449 is about 4641.0611933048. The cubic root of 21539449 is about 278.2348523509.

The spelling of 21539449 in words is "twenty-one million, five hundred thirty-nine thousand, four hundred forty-nine".