1691991961 has 4 divisors (see below), whose sum is σ = 1845809424. Its totient is φ = 1538174500.

The previous prime is 1691991923. The next prime is 1691991989.

1691991961 is nontrivially palindromic in base 10.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1691991961 - 2¹⁵ = 1691959193 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1691991899 and 1691991908.

It is not an unprimeable number, because it can be changed into a prime (1691991991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 76908715 + ... + 76908736.

It is an arithmetic number, because the mean of its divisors is an integer number (461452356).

Almost surely, 2^1691991961 is an apocalyptic number.

1691991961 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1691991961 is a deficient number, since it is larger than the sum of its proper divisors (153817463).

1691991961 is a wasteful number, since it uses less digits than its factorization.

1691991961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 153817462.

The product of its digits is 236196, while the sum is 52.

The square root of 1691991961 is about 41133.8298849013. The cubic root of 1691991961 is about 1191.6062298678.

The spelling of 1691991961 in words is "one billion, six hundred ninety-one million, nine hundred ninety-one thousand, nine hundred sixty-one".