991973 has 2 divisors, whose sum is σ = 991974. Its totient is φ = 991972.

The previous prime is 991961. The next prime is 991979. The reversal of 991973 is 379199.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 833569 + 158404 = 913^2 + 398^2 .

It is an emirp because it is prime and its reverse (379199) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 991973 - 2⁴ = 991957 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991979) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495986 + 495987.

It is an arithmetic number, because the mean of its divisors is an integer number (495987).

2⁹⁹¹⁹⁷³ is an apocalyptic number.

It is an amenable number.

991973 is a deficient number, since it is larger than the sum of its proper divisors (1).

991973 is an equidigital number, since it uses as much as digits as its factorization.

991973 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15309, while the sum is 38.

The square root of 991973 is about 995.9784134207. The cubic root of 991973 is about 99.7317142043.

The spelling of 991973 in words is "nine hundred ninety-one thousand, nine hundred seventy-three".