21951680 has 56 divisors (see below), whose sum is σ = 52699920. Its totient is φ = 8709120.

The previous prime is 21951667. The next prime is 21951691. The reversal of 21951680 is 8615912.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 57731 + ... + 58109.

It is an arithmetic number, because the mean of its divisors is an integer number (941070).

Almost surely, 2^21951680 is an apocalyptic number.

21951680 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 21951680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26349960).

21951680 is an abundant number, since it is smaller than the sum of its proper divisors (30748240).

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

21951680 is a wasteful number, since it uses less digits than its factorization.

21951680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 577 (or 567 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 32.

The square root of 21951680 is about 4685.2619990775. The cubic root of 21951680 is about 279.9986394492.

The spelling of 21951680 in words is "twenty-one million, nine hundred fifty-one thousand, six hundred eighty".