21556740 has 24 divisors (see below), whose sum is σ = 60359040. Its totient is φ = 5748448.

The previous prime is 21556739. The next prime is 21556753. The reversal of 21556740 is 4765512.

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 = 21556698 and 21556707.

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, 179580 + ... + 179699.

It is an arithmetic number, because the mean of its divisors is an integer number (2514960).

Almost surely, 2^21556740 is an apocalyptic number.

21556740 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21556740 is an abundant number, since it is smaller than the sum of its proper divisors (38802300).

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

21556740 is a wasteful number, since it uses less digits than its factorization.

21556740 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 359291 (or 359289 counting only the distinct ones).

The product of its (nonzero) digits is 8400, while the sum is 30.

The square root of 21556740 is about 4642.9236478753. The cubic root of 21556740 is about 278.3092843393.

The spelling of 21556740 in words is "twenty-one million, five hundred fifty-six thousand, seven hundred forty".