91971720 has 64 divisors (see below), whose sum is σ = 306576000. Its totient is φ = 24525504.

The previous prime is 91971701. The next prime is 91971739. The reversal of 91971720 is 2717919.

It is an interprime number because it is at equal distance from previous prime (91971701) and next prime (91971739).

It is a super-3 number, since 3×91971720³ (a number of 25 digits) contains 333 as substring.

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

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 41500 + ... + 43659.

It is an arithmetic number, because the mean of its divisors is an integer number (4790250).

Almost surely, 2^91971720 is an apocalyptic number.

91971720 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is an amenable number.

91971720 is an abundant number, since it is smaller than the sum of its proper divisors (214604280).

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

91971720 is a wasteful number, since it uses less digits than its factorization.

91971720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85179 (or 85169 counting only the distinct ones).

The product of its (nonzero) digits is 7938, while the sum is 36.

The square root of 91971720 is about 9590.1887364118. The cubic root of 91971720 is about 451.3894829997.

The spelling of 91971720 in words is "ninety-one million, nine hundred seventy-one thousand, seven hundred twenty".