21973680 has 100 divisors (see below), whose sum is σ = 76340352. Its totient is φ = 5857920.

The previous prime is 21973649. The next prime is 21973681. The reversal of 21973680 is 8637912.

It is a super-2 number, since 2×21973680² = 965685225484800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (21973681) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 4785 + ... + 8175.

Almost surely, 2^21973680 is an apocalyptic number.

21973680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21973680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38170176).

21973680 is an abundant number, since it is smaller than the sum of its proper divisors (54366672).

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

21973680 is a wasteful number, since it uses less digits than its factorization.

21973680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3416 (or 3401 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 21973680 is about 4687.6091987281. The cubic root of 21973680 is about 280.0921465425.

The spelling of 21973680 in words is "twenty-one million, nine hundred seventy-three thousand, six hundred eighty".