21173680 has 40 divisors (see below), whose sum is σ = 53706384. Its totient is φ = 7699200.

The previous prime is 21173629. The next prime is 21173689. The reversal of 21173680 is 8637112.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Smith number, since the sum of its digits (28) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (21173689) 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, 11151 + ... + 12910.

Almost surely, 2^21173680 is an apocalyptic number.

21173680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21173680 is an abundant number, since it is smaller than the sum of its proper divisors (32532704).

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

21173680 is a wasteful number, since it uses less digits than its factorization.

21173680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24085 (or 24079 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 21173680 is about 4601.4867162690. The cubic root of 21173680 is about 276.6509176371.

The spelling of 21173680 in words is "twenty-one million, one hundred seventy-three thousand, six hundred eighty".