21186840 has 32 divisors (see below), whose sum is σ = 63560880. Its totient is φ = 5649792.

The previous prime is 21186839. The next prime is 21186859. The reversal of 21186840 is 4868112.

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

It is a junction number, because it is equal to n+sod(n) for n = 21186798 and 21186807.

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, 88159 + ... + 88398.

Almost surely, 2^21186840 is an apocalyptic number.

21186840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21186840 is an abundant number, since it is smaller than the sum of its proper divisors (42374040).

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

21186840 is a wasteful number, since it uses less digits than its factorization.

21186840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 176571 (or 176567 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 30.

The square root of 21186840 is about 4602.9164667632. The cubic root of 21186840 is about 276.7082210450.

The spelling of 21186840 in words is "twenty-one million, one hundred eighty-six thousand, eight hundred forty".