21768057 has 6 divisors (see below), whose sum is σ = 31442762. Its totient is φ = 14512032.

The previous prime is 21768049. The next prime is 21768059. The reversal of 21768057 is 75086712.

It can be written as a sum of positive squares in only one way, i.e., 12257001 + 9511056 = 3501^2 + 3084^2 .

It is not a de Polignac number, because 21768057 - 2³ = 21768049 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21768059) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1209328 + ... + 1209345.

Almost surely, 2^21768057 is an apocalyptic number.

It is an amenable number.

21768057 is a deficient number, since it is larger than the sum of its proper divisors (9674705).

21768057 is a wasteful number, since it uses less digits than its factorization.

21768057 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2418679 (or 2418676 counting only the distinct ones).

The product of its (nonzero) digits is 23520, while the sum is 36.

The square root of 21768057 is about 4665.6250385131. The cubic root of 21768057 is about 279.2157347873.

The spelling of 21768057 in words is "twenty-one million, seven hundred sixty-eight thousand, fifty-seven".