21520531420 has 24 divisors (see below), whose sum is σ = 45206664048. Its totient is φ = 8605632000.

The previous prime is 21520531411. The next prime is 21520531423. The reversal of 21520531420 is 2413502512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21520531423) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 92181 + ... + 227020.

It is an arithmetic number, because the mean of its divisors is an integer number (1883611002).

Almost surely, 2^21520531420 is an apocalyptic number.

21520531420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21520531420 is an abundant number, since it is smaller than the sum of its proper divisors (23686132628).

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

21520531420 is a wasteful number, since it uses less digits than its factorization.

21520531420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322581 (or 322579 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 25.

The spelling of 21520531420 in words is "twenty-one billion, five hundred twenty million, five hundred thirty-one thousand, four hundred twenty".