21660858 has 20 divisors (see below), whose sum is σ = 48536730. Its totient is φ = 7220232.

The previous prime is 21660853. The next prime is 21660901. The reversal of 21660858 is 85806612.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 12131289 + 9529569 = 3483^2 + 3087^2 .

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21660851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 66693 + ... + 67016.

Almost surely, 2^21660858 is an apocalyptic number.

21660858 is an abundant number, since it is smaller than the sum of its proper divisors (26875872).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21660858 is a wasteful number, since it uses less digits than its factorization.

21660858 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133723 (or 133714 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 36.

The square root of 21660858 is about 4654.1226885418. The cubic root of 21660858 is about 278.7566382890.

The spelling of 21660858 in words is "twenty-one million, six hundred sixty thousand, eight hundred fifty-eight".