21128449 has 2 divisors, whose sum is σ = 21128450. Its totient is φ = 21128448.

The previous prime is 21128441. The next prime is 21128461. The reversal of 21128449 is 94482112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19847025 + 1281424 = 4455^2 + 1132^2 .

It is a cyclic number.

It is not a de Polignac number, because 21128449 - 2³ = 21128441 is a prime.

It is a super-2 number, since 2×21128449² = 892822714291202, 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 21128449.

It is not a weakly prime, because it can be changed into another prime (21128441) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10564224 + 10564225.

It is an arithmetic number, because the mean of its divisors is an integer number (10564225).

Almost surely, 2^21128449 is an apocalyptic number.

It is an amenable number.

21128449 is a deficient number, since it is larger than the sum of its proper divisors (1).

21128449 is an equidigital number, since it uses as much as digits as its factorization.

21128449 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4608, while the sum is 31.

The square root of 21128449 is about 4596.5692641360. The cubic root of 21128449 is about 276.4537842395.

The spelling of 21128449 in words is "twenty-one million, one hundred twenty-eight thousand, four hundred forty-nine".