21251235125 has 8 divisors (see below), whose sum is σ = 26521541592. Its totient is φ = 17000988000.

The previous prime is 21251235079. The next prime is 21251235143. The reversal of 21251235125 is 52153215212.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 7006609 + 21244228516 = 2647^2 + 145754^2 .

It is not a de Polignac number, because 21251235125 - 2¹⁴ = 21251218741 is a prime.

It is a super-2 number, since 2×21251235125² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

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, 85004816 + ... + 85005065.

It is an arithmetic number, because the mean of its divisors is an integer number (3315192699).

Almost surely, 2^21251235125 is an apocalyptic number.

21251235125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21251235125 is a deficient number, since it is larger than the sum of its proper divisors (5270306467).

21251235125 is an equidigital number, since it uses as much as digits as its factorization.

21251235125 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 170009896 (or 170009886 counting only the distinct ones).

The product of its digits is 6000, while the sum is 29.

The spelling of 21251235125 in words is "twenty-one billion, two hundred fifty-one million, two hundred thirty-five thousand, one hundred twenty-five".