21405522540 has 24 divisors (see below), whose sum is σ = 59935463280. Its totient is φ = 5708139328.

The previous prime is 21405522533. The next prime is 21405522577. The reversal of 21405522540 is 4522550412.

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 = 21405522498 and 21405522507.

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, 178379295 + ... + 178379414.

It is an arithmetic number, because the mean of its divisors is an integer number (2497310970).

Almost surely, 2^21405522540 is an apocalyptic number.

21405522540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21405522540 is an abundant number, since it is smaller than the sum of its proper divisors (38529940740).

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

21405522540 is a wasteful number, since it uses less digits than its factorization.

21405522540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 356758721 (or 356758719 counting only the distinct ones).

The product of its (nonzero) digits is 16000, while the sum is 30.

The spelling of 21405522540 in words is "twenty-one billion, four hundred five million, five hundred twenty-two thousand, five hundred forty".