21680144 has 20 divisors (see below), whose sum is σ = 43031100. Its totient is φ = 10575360.

The previous prime is 21680143. The next prime is 21680149. The reversal of 21680144 is 44108612.

It can be written as a sum of positive squares in 2 ways, for example, as 409600 + 21270544 = 640^2 + 4612^2 .

It is a hoax number, since the sum of its digits (26) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21680143) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15869 + ... + 17180.

It is an arithmetic number, because the mean of its divisors is an integer number (2151555).

Almost surely, 2^21680144 is an apocalyptic number.

It is an amenable number.

21680144 is a deficient number, since it is larger than the sum of its proper divisors (21350956).

21680144 is a wasteful number, since it uses less digits than its factorization.

21680144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33098 (or 33092 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 26.

The square root of 21680144 is about 4656.1941540275. The cubic root of 21680144 is about 278.8393451660.

Adding to 21680144 its reverse (44108612), we get a palindrome (65788756).

The spelling of 21680144 in words is "twenty-one million, six hundred eighty thousand, one hundred forty-four".