21231125440 has 56 divisors (see below), whose sum is σ = 57778997472. Its totient is φ = 7279242240.

The previous prime is 21231125411. The next prime is 21231125459. The reversal of 21231125440 is 4452113212.

It is a tau number, because it is divible by the number of its divisors (56).

It is a congruent number.

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, 4736851 + ... + 4741330.

It is an arithmetic number, because the mean of its divisors is an integer number (1031767812).

Almost surely, 2^21231125440 is an apocalyptic number.

21231125440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21231125440 is an abundant number, since it is smaller than the sum of its proper divisors (36547872032).

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

21231125440 is an equidigital number, since it uses as much as digits as its factorization.

21231125440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9478205 (or 9478195 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 25.

Adding to 21231125440 its reverse (4452113212), we get a palindrome (25683238652).

The spelling of 21231125440 in words is "twenty-one billion, two hundred thirty-one million, one hundred twenty-five thousand, four hundred forty".