99991997 has 6 divisors (see below), whose sum is σ = 116317278. Its totient is φ = 85707384.

The previous prime is 99991987. The next prime is 99991999. The reversal of 99991997 is 79919999.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 98525476 + 1466521 = 9926^2 + 1211^2 .

It is not a de Polignac number, because 99991997 - 2⁴ = 99991981 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99991999) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1020278 + ... + 1020375.

It is an arithmetic number, because the mean of its divisors is an integer number (19386213).

Almost surely, 2^99991997 is an apocalyptic number.

It is an amenable number.

99991997 is a deficient number, since it is larger than the sum of its proper divisors (16325281).

99991997 is a wasteful number, since it uses less digits than its factorization.

99991997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2040667 (or 2040660 counting only the distinct ones).

The product of its digits is 3720087, while the sum is 62.

The square root of 99991997 is about 9999.5998419937. The cubic root of 99991997 is about 464.1465008191.

The spelling of 99991997 in words is "ninety-nine million, nine hundred ninety-one thousand, nine hundred ninety-seven".