21184857 has 6 divisors (see below), whose sum is σ = 30600362. Its totient is φ = 14123232.

The previous prime is 21184747. The next prime is 21184859. The reversal of 21184857 is 75848112.

It can be written as a sum of positive squares in only one way, i.e., 20331081 + 853776 = 4509^2 + 924^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21184857 is a prime.

It is a super-2 number, since 2×21184857² = 897596332220898, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21184859) 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, 1176928 + ... + 1176945.

Almost surely, 2^21184857 is an apocalyptic number.

It is an amenable number.

21184857 is a deficient number, since it is larger than the sum of its proper divisors (9415505).

21184857 is a wasteful number, since it uses less digits than its factorization.

21184857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2353879 (or 2353876 counting only the distinct ones).

The product of its digits is 17920, while the sum is 36.

The square root of 21184857 is about 4602.7010548155. The cubic root of 21184857 is about 276.6995878633.

The spelling of 21184857 in words is "twenty-one million, one hundred eighty-four thousand, eight hundred fifty-seven".