21545373825 has 72 divisors (see below), whose sum is σ = 40275513720. Its totient is φ = 10996070400.

The previous prime is 21545373803. The next prime is 21545373853. The reversal of 21545373825 is 52837354512.

21545373825 is a `hidden beast` number, since 21 + 545 + 3 + 7 + 3 + 82 + 5 = 666.

It can be written as a sum of positive squares in 12 ways, for example, as 18149747841 + 3395625984 = 134721^2 + 58272^2 .

It is not a de Polignac number, because 21545373825 - 2⁷ = 21545373697 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 722715 + ... + 751935.

It is an arithmetic number, because the mean of its divisors is an integer number (559382135).

Almost surely, 2^21545373825 is an apocalyptic number.

21545373825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21545373825 is a deficient number, since it is larger than the sum of its proper divisors (18730139895).

21545373825 is a wasteful number, since it uses less digits than its factorization.

21545373825 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29379 (or 29371 counting only the distinct ones).

The product of its digits is 1008000, while the sum is 45.

The spelling of 21545373825 in words is "twenty-one billion, five hundred forty-five million, three hundred seventy-three thousand, eight hundred twenty-five".