1991864711 has 4 divisors (see below), whose sum is σ = 1992136800. Its totient is φ = 1991592624.

The previous prime is 1991864663. The next prime is 1991864713. The reversal of 1991864711 is 1174681991.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1991864711 - 2²² = 1987670407 is a prime.

It is a super-2 number, since 2×1991864711² = 7935050053854227042, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991864713) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 124751 + ... + 139808.

It is an arithmetic number, because the mean of its divisors is an integer number (498034200).

Almost surely, 2^1991864711 is an apocalyptic number.

1991864711 is a deficient number, since it is larger than the sum of its proper divisors (272089).

1991864711 is an equidigital number, since it uses as much as digits as its factorization.

1991864711 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 272088.

The product of its digits is 108864, while the sum is 47.

The square root of 1991864711 is about 44630.3115718454. The cubic root of 1991864711 is about 1258.2104247460.

The spelling of 1991864711 in words is "one billion, nine hundred ninety-one million, eight hundred sixty-four thousand, seven hundred eleven".