21137880 has 128 divisors (see below), whose sum is σ = 68198400. Its totient is φ = 5225472.

The previous prime is 21137863. The next prime is 21137887. The reversal of 21137880 is 8873112.

It is a happy number.

It is a super-3 number, since 3×21137880³ (a number of 23 digits) contains 333 as substring.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21137887) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 166377 + ... + 166503.

It is an arithmetic number, because the mean of its divisors is an integer number (532800).

Almost surely, 2^21137880 is an apocalyptic number.

21137880 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 21137880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34099200).

21137880 is an abundant number, since it is smaller than the sum of its proper divisors (47060520).

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

21137880 is a wasteful number, since it uses less digits than its factorization.

21137880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 233 (or 229 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 30.

The square root of 21137880 is about 4597.5950234878. The cubic root of 21137880 is about 276.4949112181.

The spelling of 21137880 in words is "twenty-one million, one hundred thirty-seven thousand, eight hundred eighty".