21546809125 has 8 divisors (see below), whose sum is σ = 26890417944. Its totient is φ = 17237447200.

The previous prime is 21546809113. The next prime is 21546809149. The reversal of 21546809125 is 52190864512.

It can be written as a sum of positive squares in 4 ways, for example, as 4518125089 + 17028684036 = 67217^2 + 130494^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21546809125 is a prime.

It is a hoax number, since the sum of its digits (43) coincides with the sum of the digits of its distinct prime factors.

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, 86187112 + ... + 86187361.

It is an arithmetic number, because the mean of its divisors is an integer number (3361302243).

Almost surely, 2^21546809125 is an apocalyptic number.

21546809125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21546809125 is a deficient number, since it is larger than the sum of its proper divisors (5343608819).

21546809125 is an equidigital number, since it uses as much as digits as its factorization.

21546809125 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 172374488 (or 172374478 counting only the distinct ones).

The product of its (nonzero) digits is 172800, while the sum is 43.

The spelling of 21546809125 in words is "twenty-one billion, five hundred forty-six million, eight hundred nine thousand, one hundred twenty-five".