991099973 has 2 divisors, whose sum is σ = 991099974. Its totient is φ = 991099972.

The previous prime is 991099961. The next prime is 991100081. The reversal of 991099973 is 379990199.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 764356609 + 226743364 = 27647^2 + 15058^2 .

It is a cyclic number.

It is not a de Polignac number, because 991099973 - 2¹² = 991095877 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991099943) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495549986 + 495549987.

It is an arithmetic number, because the mean of its divisors is an integer number (495549987).

Almost surely, 2^991099973 is an apocalyptic number.

It is an amenable number.

991099973 is a deficient number, since it is larger than the sum of its proper divisors (1).

991099973 is an equidigital number, since it uses as much as digits as its factorization.

991099973 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1240029, while the sum is 56.

The square root of 991099973 is about 31481.7403108532. The cubic root of 991099973 is about 997.0244793919.

The spelling of 991099973 in words is "nine hundred ninety-one million, ninety-nine thousand, nine hundred seventy-three".