21085860 has 48 divisors (see below), whose sum is σ = 59665536. Its totient is φ = 5563392.

The previous prime is 21085853. The next prime is 21085879. The reversal of 21085860 is 6858012.

It is a super-2 number, since 2×21085860² = 889226983879200, which contains 22 as substring.

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

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4009 + ... + 7631.

It is an arithmetic number, because the mean of its divisors is an integer number (1243032).

Almost surely, 2^21085860 is an apocalyptic number.

21085860 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 21085860, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29832768).

21085860 is an abundant number, since it is smaller than the sum of its proper divisors (38579676).

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

21085860 is a wasteful number, since it uses less digits than its factorization.

21085860 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3732 (or 3730 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 30.

The square root of 21085860 is about 4591.9342329785. The cubic root of 21085860 is about 276.2679083140.

It can be divided in two parts, 21085 and 860, that added together give a triangular number (21945 = T₂₀₉).

The spelling of 21085860 in words is "twenty-one million, eighty-five thousand, eight hundred sixty".