21012340520 has 32 divisors (see below), whose sum is σ = 47283517800. Its totient is φ = 8403913728.

The previous prime is 21012340511. The next prime is 21012340537. The reversal of 21012340520 is 2504321012.

It can be written as a sum of positive squares in 4 ways, for example, as 13001016484 + 8011324036 = 114022^2 + 89506^2 .

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21012340492 and 21012340501.

It is an unprimeable number.

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, 360452 + ... + 414668.

Almost surely, 2^21012340520 is an apocalyptic number.

21012340520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21012340520 is an abundant number, since it is smaller than the sum of its proper divisors (26271177280).

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

21012340520 is a wasteful number, since it uses less digits than its factorization.

21012340520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63917 (or 63913 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 20.

Adding to 21012340520 its reverse (2504321012), we get a palindrome (23516661532).

The spelling of 21012340520 in words is "twenty-one billion, twelve million, three hundred forty thousand, five hundred twenty".