21357540 has 48 divisors (see below), whose sum is σ = 66447360. Its totient is φ = 5695200.

The previous prime is 21357529. The next prime is 21357563. The reversal of 21357540 is 4575312.

It is a happy number.

It is a super-2 number, since 2×21357540² = 912289029703200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

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 15 ways as a sum of consecutive naturals, for example, 19236 + ... + 20315.

It is an arithmetic number, because the mean of its divisors is an integer number (1384320).

Almost surely, 2^21357540 is an apocalyptic number.

21357540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21357540 is an abundant number, since it is smaller than the sum of its proper divisors (45089820).

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

21357540 is a wasteful number, since it uses less digits than its factorization.

21357540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39569 (or 39561 counting only the distinct ones).

The product of its (nonzero) digits is 4200, while the sum is 27.

The square root of 21357540 is about 4621.4218591252. The cubic root of 21357540 is about 277.4493698719.

The spelling of 21357540 in words is "twenty-one million, three hundred fifty-seven thousand, five hundred forty".