1991747523 has 16 divisors (see below), whose sum is σ = 2959873920. Its totient is φ = 1183948416.

The previous prime is 1991747509. The next prime is 1991747533. The reversal of 1991747523 is 3257471991.

It is not a de Polignac number, because 1991747523 - 2⁴ = 1991747507 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1991747503) 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, 1026765 + ... + 1028702.

It is an arithmetic number, because the mean of its divisors is an integer number (184992120).

Almost surely, 2^1991747523 is an apocalyptic number.

1991747523 is a deficient number, since it is larger than the sum of its proper divisors (968126397).

1991747523 is a wasteful number, since it uses less digits than its factorization.

1991747523 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2055506.

The product of its digits is 476280, while the sum is 48.

The square root of 1991747523 is about 44628.9986779896. The cubic root of 1991747523 is about 1258.1857493662.

The spelling of 1991747523 in words is "one billion, nine hundred ninety-one million, seven hundred forty-seven thousand, five hundred twenty-three".