81968400 has 90 divisors (see below), whose sum is σ = 284465610. Its totient is φ = 21857280.

The previous prime is 81968399. The next prime is 81968401. The reversal of 81968400 is 486918.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (81968399) and next prime (81968401).

It can be written as a sum of positive squares in 3 ways, for example, as 535824 + 81432576 = 732^2 + 9024^2 .

It is a tau number, because it is divible by the number of its divisors (90).

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (81968401) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 7785 + ... + 14984.

It is an arithmetic number, because the mean of its divisors is an integer number (3160729).

Almost surely, 2^81968400 is an apocalyptic number.

81968400 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81968400 is an abundant number, since it is smaller than the sum of its proper divisors (202497210).

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

81968400 is a wasteful number, since it uses less digits than its factorization.

81968400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22793 (or 22779 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 36.

The square root of 81968400 is about 9053.6401518947. The cubic root of 81968400 is about 434.3923342461.

The spelling of 81968400 in words is "eighty-one million, nine hundred sixty-eight thousand, four hundred".