21871880 has 32 divisors (see below), whose sum is σ = 49383000. Its totient is φ = 8718336.

The previous prime is 21871849. The next prime is 21871903. The reversal of 21871880 is 8817812.

It can be written as a sum of positive squares in 4 ways, for example, as 15038884 + 6832996 = 3878^2 + 2614^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21871880.

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, 13346 + ... + 14894.

Almost surely, 2^21871880 is an apocalyptic number.

21871880 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21871880 is an abundant number, since it is smaller than the sum of its proper divisors (27511120).

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

21871880 is a wasteful number, since it uses less digits than its factorization.

21871880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1913 (or 1909 counting only the distinct ones).

The product of its (nonzero) digits is 7168, while the sum is 35.

The square root of 21871880 is about 4676.7381795435. The cubic root of 21871880 is about 279.6589384710.

The spelling of 21871880 in words is "twenty-one million, eight hundred seventy-one thousand, eight hundred eighty".