21056434520 has 48 divisors (see below), whose sum is σ = 52075532880. Its totient is φ = 7656883520.

The previous prime is 21056434457. The next prime is 21056434523. The reversal of 21056434520 is 2543465012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21056434523) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2170412 + ... + 2180091.

It is an arithmetic number, because the mean of its divisors is an integer number (1084906935).

Almost surely, 2^21056434520 is an apocalyptic number.

21056434520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21056434520 is an abundant number, since it is smaller than the sum of its proper divisors (31019098360).

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

21056434520 is a wasteful number, since it uses less digits than its factorization.

21056434520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4350536 (or 4350521 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 32.

Adding to 21056434520 its reverse (2543465012), we get a palindrome (23599899532).

The spelling of 21056434520 in words is "twenty-one billion, fifty-six million, four hundred thirty-four thousand, five hundred twenty".