99371981 has 4 divisors (see below), whose sum is σ = 100355964. Its totient is φ = 98388000.

The previous prime is 99371977. The next prime is 99372023. The reversal of 99371981 is 18917399.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18917399 = 347 ⋅54517.

It can be written as a sum of positive squares in 2 ways, for example, as 94381225 + 4990756 = 9715^2 + 2234^2 .

It is a cyclic number.

It is not a de Polignac number, because 99371981 - 2² = 99371977 is a prime.

It is a super-2 number, since 2×99371981² = 19749581215728722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99371911) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 491840 + ... + 492041.

It is an arithmetic number, because the mean of its divisors is an integer number (25088991).

Almost surely, 2^99371981 is an apocalyptic number.

It is an amenable number.

99371981 is a deficient number, since it is larger than the sum of its proper divisors (983983).

99371981 is a wasteful number, since it uses less digits than its factorization.

99371981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 983982.

The product of its digits is 122472, while the sum is 47.

The square root of 99371981 is about 9968.5495935969. The cubic root of 99371981 is about 463.1851734873.

The spelling of 99371981 in words is "ninety-nine million, three hundred seventy-one thousand, nine hundred eighty-one".