21683640 has 64 divisors (see below), whose sum is σ = 70968960. Its totient is φ = 5256320.

The previous prime is 21683611. The next prime is 21683659. The reversal of 21683640 is 4638612.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 21683598 and 21683607.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6894 + ... + 9533.

It is an arithmetic number, because the mean of its divisors is an integer number (1108890).

Almost surely, 2^21683640 is an apocalyptic number.

21683640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21683640 is an abundant number, since it is smaller than the sum of its proper divisors (49285320).

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

21683640 is a wasteful number, since it uses less digits than its factorization.

21683640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16452 (or 16448 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 30.

The square root of 21683640 is about 4656.5695527931. The cubic root of 21683640 is about 278.8543323044.

The spelling of 21683640 in words is "twenty-one million, six hundred eighty-three thousand, six hundred forty".