21806880 has 96 divisors (see below), whose sum is σ = 69346368. Its totient is φ = 5760000.

The previous prime is 21806879. The next prime is 21806881. The reversal of 21806880 is 8860812.

21806880 = T₂₈₅ + T₂₈₆ + ... + T₅₃₅.

It is an interprime number because it is at equal distance from previous prime (21806879) and next prime (21806881).

It is a tau number, because it is divible by the number of its divisors (96).

It is not an unprimeable number, because it can be changed into a prime (21806881) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 86755 + ... + 87005.

It is an arithmetic number, because the mean of its divisors is an integer number (722358).

Almost surely, 2^21806880 is an apocalyptic number.

21806880 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 21806880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34673184).

21806880 is an abundant number, since it is smaller than the sum of its proper divisors (47539488).

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

21806880 is a wasteful number, since it uses less digits than its factorization.

21806880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 450 (or 442 counting only the distinct ones).

The product of its (nonzero) digits is 6144, while the sum is 33.

The square root of 21806880 is about 4669.7837209019. The cubic root of 21806880 is about 279.3816285481.

The spelling of 21806880 in words is "twenty-one million, eight hundred six thousand, eight hundred eighty".