21251255520 has 192 divisors, whose sum is σ = 73193186304. Its totient is φ = 5140101120.

The previous prime is 21251255453. The next prime is 21251255533. The reversal of 21251255520 is 2555215212.

It is a super-2 number, since 2×21251255520² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2440294 + ... + 2448986.

It is an arithmetic number, because the mean of its divisors is an integer number (381214512).

Almost surely, 2^21251255520 is an apocalyptic number.

21251255520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21251255520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36596593152).

21251255520 is an abundant number, since it is smaller than the sum of its proper divisors (51941930784).

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

21251255520 is a wasteful number, since it uses less digits than its factorization.

21251255520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9185 (or 9177 counting only the distinct ones).

The product of its (nonzero) digits is 10000, while the sum is 30.

The spelling of 21251255520 in words is "twenty-one billion, two hundred fifty-one million, two hundred fifty-five thousand, five hundred twenty".