21187040 has 48 divisors (see below), whose sum is σ = 57208032. Its totient is φ = 7263744.

The previous prime is 21187027. The next prime is 21187063. The reversal of 21187040 is 4078112.

It is a junction number, because it is equal to n+sod(n) for n = 21186997 and 21187015.

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, 8339 + ... + 10578.

It is an arithmetic number, because the mean of its divisors is an integer number (1191834).

Almost surely, 2^21187040 is an apocalyptic number.

21187040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21187040 is an abundant number, since it is smaller than the sum of its proper divisors (36020992).

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

21187040 is a wasteful number, since it uses less digits than its factorization.

21187040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18939 (or 18931 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 23.

The square root of 21187040 is about 4602.9381920682. The cubic root of 21187040 is about 276.7090917344.

The spelling of 21187040 in words is "twenty-one million, one hundred eighty-seven thousand, forty".