21173290 has 16 divisors (see below), whose sum is σ = 38175912. Its totient is φ = 8455104.

The previous prime is 21173263. The next prime is 21173291. The reversal of 21173290 is 9237112.

It can be written as a sum of positive squares in 4 ways, for example, as 19562929 + 1610361 = 4423^2 + 1269^2 .

It is not an unprimeable number, because it can be changed into a prime (21173291) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6172 + ... + 8968.

Almost surely, 2^21173290 is an apocalyptic number.

21173290 is a deficient number, since it is larger than the sum of its proper divisors (17002622).

21173290 is a wasteful number, since it uses less digits than its factorization.

21173290 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3561.

The product of its (nonzero) digits is 756, while the sum is 25.

The square root of 21173290 is about 4601.4443384659. Note that the first 3 decimals coincide. The cubic root of 21173290 is about 276.6492190736.

The spelling of 21173290 in words is "twenty-one million, one hundred seventy-three thousand, two hundred ninety".