21138853825 has 6 divisors (see below), whose sum is σ = 26212178774. Its totient is φ = 16911083040.

The previous prime is 21138853781. The next prime is 21138853861. The reversal of 21138853825 is 52835883112.

It can be written as a sum of positive squares in 3 ways, for example, as 419266576 + 20719587249 = 20476^2 + 143943^2 .

It is not a de Polignac number, because 21138853825 - 2¹⁷ = 21138722753 is a prime.

It is a super-2 number, since 2×21138853825² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 422777052 + ... + 422777101.

Almost surely, 2^21138853825 is an apocalyptic number.

21138853825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21138853825 is a deficient number, since it is larger than the sum of its proper divisors (5073324949).

21138853825 is an equidigital number, since it uses as much as digits as its factorization.

21138853825 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 845554163 (or 845554158 counting only the distinct ones).

The product of its digits is 460800, while the sum is 46.

The spelling of 21138853825 in words is "twenty-one billion, one hundred thirty-eight million, eight hundred fifty-three thousand, eight hundred twenty-five".