21255417 has 6 divisors (see below), whose sum is σ = 30702282. Its totient is φ = 14170272.

The previous prime is 21255407. The next prime is 21255419. The reversal of 21255417 is 71455212.

It can be written as a sum of positive squares in only one way, i.e., 19900521 + 1354896 = 4461^2 + 1164^2 .

It is not a de Polignac number, because 21255417 - 2⁴ = 21255401 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21255419) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1180848 + ... + 1180865.

It is an arithmetic number, because the mean of its divisors is an integer number (5117047).

Almost surely, 2^21255417 is an apocalyptic number.

It is an amenable number.

21255417 is a deficient number, since it is larger than the sum of its proper divisors (9446865).

21255417 is a wasteful number, since it uses less digits than its factorization.

21255417 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2361719 (or 2361716 counting only the distinct ones).

The product of its digits is 2800, while the sum is 27.

The square root of 21255417 is about 4610.3597473516. The cubic root of 21255417 is about 277.0064467822.

The spelling of 21255417 in words is "twenty-one million, two hundred fifty-five thousand, four hundred seventeen".