21173687 has 8 divisors (see below), whose sum is σ = 22540032. Its totient is φ = 19820800.

The previous prime is 21173629. The next prime is 21173689. The reversal of 21173687 is 78637112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21173687 - 2⁶ = 21173623 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21173689) 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 7 ways as a sum of consecutive naturals, for example, 14 + ... + 6507.

It is an arithmetic number, because the mean of its divisors is an integer number (2817504).

Almost surely, 2^21173687 is an apocalyptic number.

21173687 is a deficient number, since it is larger than the sum of its proper divisors (1366345).

21173687 is a wasteful number, since it uses less digits than its factorization.

21173687 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6729.

The product of its digits is 14112, while the sum is 35.

The square root of 21173687 is about 4601.4874768927. The cubic root of 21173687 is about 276.6509481239.

The spelling of 21173687 in words is "twenty-one million, one hundred seventy-three thousand, six hundred eighty-seven".