21545540 has 24 divisors (see below), whose sum is σ = 45689280. Its totient is φ = 8533728.

The previous prime is 21545509. The next prime is 21545551. The reversal of 21545540 is 4554512.

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, 3170 + ... + 7289.

It is an arithmetic number, because the mean of its divisors is an integer number (1903720).

Almost surely, 2^21545540 is an apocalyptic number.

21545540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21545540 is an abundant number, since it is smaller than the sum of its proper divisors (24143740).

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

21545540 is a wasteful number, since it uses less digits than its factorization.

21545540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10571 (or 10569 counting only the distinct ones).

The product of its (nonzero) digits is 4000, while the sum is 26.

The square root of 21545540 is about 4641.7173546006. The cubic root of 21545540 is about 278.2610766175.

The spelling of 21545540 in words is "twenty-one million, five hundred forty-five thousand, five hundred forty".