21487860 has 144 divisors (see below), whose sum is σ = 70412160. Its totient is φ = 5287680.

The previous prime is 21487783. The next prime is 21487891. The reversal of 21487860 is 6878412.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 208569 + ... + 208671.

Almost surely, 2^21487860 is an apocalyptic number.

21487860 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is a pronic number, being equal to 4635×4636.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21487860, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35206080).

21487860 is an abundant number, since it is smaller than the sum of its proper divisors (48924300).

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

21487860 is a wasteful number, since it uses less digits than its factorization.

21487860 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 198 (or 193 counting only the distinct ones).

The product of its (nonzero) digits is 21504, while the sum is 36.

The square root of 21487860 is about 4635.4999730342. The cubic root of 21487860 is about 278.0125419182.

The spelling of 21487860 in words is "twenty-one million, four hundred eighty-seven thousand, eight hundred sixty".