25581820 has 72 divisors (see below), whose sum is σ = 61057584. Its totient is φ = 9002400.

The previous prime is 25581779. The next prime is 25581823. The reversal of 25581820 is 2818552.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25581823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 825205 + ... + 825235.

It is an arithmetic number, because the mean of its divisors is an integer number (848022).

Almost surely, 2^25581820 is an apocalyptic number.

25581820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 25581820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30528792).

25581820 is an abundant number, since it is smaller than the sum of its proper divisors (35475764).

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

25581820 is a wasteful number, since it uses less digits than its factorization.

25581820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104 (or 49 counting only the distinct ones).

The product of its (nonzero) digits is 6400, while the sum is 31.

The square root of 25581820 is about 5057.8473681992. The cubic root of 25581820 is about 294.6527370232.

The spelling of 25581820 in words is "twenty-five million, five hundred eighty-one thousand, eight hundred twenty".