991057 has 2 divisors, whose sum is σ = 991058. Its totient is φ = 991056.

The previous prime is 991043. The next prime is 991063. The reversal of 991057 is 750199.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 968256 + 22801 = 984^2 + 151^2 .

It is a cyclic number.

It is not a de Polignac number, because 991057 - 2¹⁵ = 958289 is a prime.

991057 is a lucky number.

It is equal to p₇₇₈₅₄ and since 991057 and 77854 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (991027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495528 + 495529.

It is an arithmetic number, because the mean of its divisors is an integer number (495529).

2⁹⁹¹⁰⁵⁷ is an apocalyptic number.

It is an amenable number.

991057 is a deficient number, since it is larger than the sum of its proper divisors (1).

991057 is an equidigital number, since it uses as much as digits as its factorization.

991057 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2835, while the sum is 31.

The square root of 991057 is about 995.5184578902. The cubic root of 991057 is about 99.7010069224.

It can be divided in two parts, 99 and 1057, that added together give a square (1156 = 34²).

The spelling of 991057 in words is "nine hundred ninety-one thousand, fifty-seven".