21628553 has 2 divisors, whose sum is σ = 21628554. Its totient is φ = 21628552.

The previous prime is 21628501. The next prime is 21628567. The reversal of 21628553 is 35582612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21603904 + 24649 = 4648^2 + 157^2 .

It is a cyclic number.

It is not a de Polignac number, because 21628553 - 2²⁴ = 4851337 is a prime.

It is not a weakly prime, because it can be changed into another prime (21628583) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10814276 + 10814277.

It is an arithmetic number, because the mean of its divisors is an integer number (10814277).

Almost surely, 2^21628553 is an apocalyptic number.

It is an amenable number.

21628553 is a deficient number, since it is larger than the sum of its proper divisors (1).

21628553 is an equidigital number, since it uses as much as digits as its factorization.

21628553 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14400, while the sum is 32.

The square root of 21628553 is about 4650.6508146710. The cubic root of 21628553 is about 278.6179901382.

The spelling of 21628553 in words is "twenty-one million, six hundred twenty-eight thousand, five hundred fifty-three".