21213125440 has 56 divisors (see below), whose sum is σ = 54399439080. Its totient is φ = 7832537088.

The previous prime is 21213125413. The next prime is 21213125443. The reversal of 21213125440 is 4452131212.

It can be written as a sum of positive squares in 4 ways, for example, as 157954624 + 21055170816 = 12568^2 + 145104^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21213125443) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2545495 + ... + 2553814.

It is an arithmetic number, because the mean of its divisors is an integer number (971418555).

Almost surely, 2^21213125440 is an apocalyptic number.

21213125440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21213125440 is an abundant number, since it is smaller than the sum of its proper divisors (33186313640).

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

21213125440 is a wasteful number, since it uses less digits than its factorization.

21213125440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5099339 (or 5099329 counting only the distinct ones).

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

Adding to 21213125440 its reverse (4452131212), we get a palindrome (25665256652).

The spelling of 21213125440 in words is "twenty-one billion, two hundred thirteen million, one hundred twenty-five thousand, four hundred forty".