1917981691 has 4 divisors (see below), whose sum is σ = 1969819072. Its totient is φ = 1866144312.

The previous prime is 1917981677. The next prime is 1917981713. The reversal of 1917981691 is 1961897191.

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 1917981691 - 2⁹ = 1917981179 is a prime.

It is a super-2 number, since 2×1917981691² = 7357307534022438962, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1917981601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25918635 + ... + 25918708.

It is an arithmetic number, because the mean of its divisors is an integer number (492454768).

Almost surely, 2^1917981691 is an apocalyptic number.

1917981691 is a deficient number, since it is larger than the sum of its proper divisors (51837381).

1917981691 is an equidigital number, since it uses as much as digits as its factorization.

1917981691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51837380.

The product of its digits is 244944, while the sum is 52.

The square root of 1917981691 is about 43794.7678495959. The cubic root of 1917981691 is about 1242.4573389021.

The spelling of 1917981691 in words is "one billion, nine hundred seventeen million, nine hundred eighty-one thousand, six hundred ninety-one".