1909597991 has 4 divisors (see below), whose sum is σ = 2182397712. Its totient is φ = 1636798272.

The previous prime is 1909597979. The next prime is 1909597993. The reversal of 1909597991 is 1997959091.

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 1909597991 - 2¹⁰ = 1909596967 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1909597991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1909597993) 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, 136399850 + ... + 136399863.

It is an arithmetic number, because the mean of its divisors is an integer number (545599428).

Almost surely, 2^1909597991 is an apocalyptic number.

1909597991 is a deficient number, since it is larger than the sum of its proper divisors (272799721).

1909597991 is an equidigital number, since it uses as much as digits as its factorization.

1909597991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 272799720.

The product of its (nonzero) digits is 2066715, while the sum is 59.

The square root of 1909597991 is about 43698.9472527657. The cubic root of 1909597991 is about 1240.6443908345.

The spelling of 1909597991 in words is "one billion, nine hundred nine million, five hundred ninety-seven thousand, nine hundred ninety-one".