991965 has 16 divisors (see below), whose sum is σ = 1709568. Its totient is φ = 488256.

The previous prime is 991961. The next prime is 991973. The reversal of 991965 is 569199.

991965 = T₄₆₅ + T₄₆₆ + ... + T₄₇₃.

It is not a de Polignac number, because 991965 - 2² = 991961 is a prime.

It is a super-2 number, since 2×991965² = 1967989122450, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a Curzon number.

991965 is a lucky number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 991965.

It is not an unprimeable number, because it can be changed into a prime (991961) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2349 + ... + 2738.

It is an arithmetic number, because the mean of its divisors is an integer number (106848).

2⁹⁹¹⁹⁶⁵ is an apocalyptic number.

It is an amenable number.

991965 is a deficient number, since it is larger than the sum of its proper divisors (717603).

991965 is a wasteful number, since it uses less digits than its factorization.

991965 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5108.

The product of its digits is 21870, while the sum is 39.

The square root of 991965 is about 995.9743972613. The cubic root of 991965 is about 99.7314461003.

The spelling of 991965 in words is "nine hundred ninety-one thousand, nine hundred sixty-five".