91997879400 has 288 divisors, whose sum is σ = 368449810560. Its totient is φ = 20113758720.

The previous prime is 91997879317. The next prime is 91997879417. The reversal of 91997879400 is 497879919.

91997879400 is a `hidden beast` number, since 9 + 1 + 99 + 78 + 79 + 400 = 666.

It is a Harshad number since it is a multiple of its sum of digits (63).

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, 131074 + ... + 448526.

It is an arithmetic number, because the mean of its divisors is an integer number (1279339620).

Almost surely, 2^91997879400 is an apocalyptic number.

91997879400 is a gapful number since it is divisible by the number (90) 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 91997879400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (184224905280).

91997879400 is an abundant number, since it is smaller than the sum of its proper divisors (276451931160).

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

91997879400 is a wasteful number, since it uses less digits than its factorization.

91997879400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 317505 (or 317493 counting only the distinct ones).

The product of its (nonzero) digits is 10287648, while the sum is 63.

The spelling of 91997879400 in words is "ninety-one billion, nine hundred ninety-seven million, eight hundred seventy-nine thousand, four hundred".