21660039 has 6 divisors (see below), whose sum is σ = 31286736. Its totient is φ = 14440020.

The previous prime is 21660011. The next prime is 21660047. The reversal of 21660039 is 93006612.

It is a happy number.

21660039 is a `hidden beast` number, since 21 + 6 + 600 + 39 = 666.

It is not a de Polignac number, because 21660039 - 2⁵ = 21660007 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21659994 and 21660021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21660239) 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, 1203327 + ... + 1203344.

It is an arithmetic number, because the mean of its divisors is an integer number (5214456).

Almost surely, 2^21660039 is an apocalyptic number.

21660039 is a deficient number, since it is larger than the sum of its proper divisors (9626697).

21660039 is a wasteful number, since it uses less digits than its factorization.

21660039 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2406677 (or 2406674 counting only the distinct ones).

The product of its (nonzero) digits is 1944, while the sum is 27.

The square root of 21660039 is about 4654.0347012028. The cubic root of 21660039 is about 278.7531249692.

The spelling of 21660039 in words is "twenty-one million, six hundred sixty thousand, thirty-nine".