21601680 has 40 divisors (see below), whose sum is σ = 66965952. Its totient is φ = 5760384.

The previous prime is 21601667. The next prime is 21601691. The reversal of 21601680 is 8610612.

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

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21601680.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 44764 + ... + 45243.

Almost surely, 2^21601680 is an apocalyptic number.

21601680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21601680 is an abundant number, since it is smaller than the sum of its proper divisors (45364272).

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

21601680 is a wasteful number, since it uses less digits than its factorization.

21601680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90023 (or 90017 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 24.

The square root of 21601680 is about 4647.7607511575. The cubic root of 21601680 is about 278.5025500789.

The spelling of 21601680 in words is "twenty-one million, six hundred one thousand, six hundred eighty".