1991377373 has 2 divisors, whose sum is σ = 1991377374. Its totient is φ = 1991377372.

The previous prime is 1991377369. The next prime is 1991377447. The reversal of 1991377373 is 3737731991.

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., 1967543449 + 23833924 = 44357^2 + 4882^2 .

It is a cyclic number.

It is not a de Polignac number, because 1991377373 - 2² = 1991377369 is a prime.

It is a super-2 number, since 2×1991377373² = 7931167683392762258, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1991377273) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995688686 + 995688687.

It is an arithmetic number, because the mean of its divisors is an integer number (995688687).

Almost surely, 2^1991377373 is an apocalyptic number.

It is an amenable number.

1991377373 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991377373 is an equidigital number, since it uses as much as digits as its factorization.

1991377373 is an evil number, because the sum of its binary digits is even.

The product of its digits is 750141, while the sum is 50.

The square root of 1991377373 is about 44624.8515179603. The cubic root of 1991377373 is about 1258.1078033577.

The spelling of 1991377373 in words is "one billion, nine hundred ninety-one million, three hundred seventy-seven thousand, three hundred seventy-three".