1991593601 has 4 divisors (see below), whose sum is σ = 1992877572. Its totient is φ = 1990309632.

The previous prime is 1991593567. The next prime is 1991593607. The reversal of 1991593601 is 1063951991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1063951991 = 1439 ⋅739369.

It can be written as a sum of positive squares in 2 ways, for example, as 594628225 + 1396965376 = 24385^2 + 37376^2 .

It is a cyclic number.

It is not a de Polignac number, because 1991593601 - 2¹⁸ = 1991331457 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991593607) 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, 639656 + ... + 642761.

It is an arithmetic number, because the mean of its divisors is an integer number (498219393).

Almost surely, 2^1991593601 is an apocalyptic number.

It is an amenable number.

1991593601 is a deficient number, since it is larger than the sum of its proper divisors (1283971).

1991593601 is a wasteful number, since it uses less digits than its factorization.

1991593601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1283970.

The product of its (nonzero) digits is 65610, while the sum is 44.

The square root of 1991593601 is about 44627.2741829478. The cubic root of 1991593601 is about 1258.1533377187.

The spelling of 1991593601 in words is "one billion, nine hundred ninety-one million, five hundred ninety-three thousand, six hundred one".