81958900 has 36 divisors (see below), whose sum is σ = 179449452. Its totient is φ = 32488960.

The previous prime is 81958879. The next prime is 81958907. The reversal of 81958900 is 985918.

It can be written as a sum of positive squares in 6 ways, for example, as 9572836 + 72386064 = 3094^2 + 8508^2 .

It is a super-2 number, since 2×81958900² = 13434522578420000, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81958907) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7674 + ... + 14926.

It is an arithmetic number, because the mean of its divisors is an integer number (4984707).

Almost surely, 2^81958900 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81958900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (89724726).

81958900 is an abundant number, since it is smaller than the sum of its proper divisors (97490552).

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

81958900 is a wasteful number, since it uses less digits than its factorization.

81958900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7380 (or 7373 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 40.

The square root of 81958900 is about 9053.1154858424. The cubic root of 81958900 is about 434.3755518168.

The spelling of 81958900 in words is "eighty-one million, nine hundred fifty-eight thousand, nine hundred".