1961551691 has 24 divisors (see below), whose sum is σ = 2234757504. Its totient is φ = 1718640000.

The previous prime is 1961551679. The next prime is 1961551733.

1961551691 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 1961551691 - 2²⁶ = 1894442827 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1961551601) 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 23 ways as a sum of consecutive naturals, for example, 1053101 + ... + 1054961.

It is an arithmetic number, because the mean of its divisors is an integer number (93114896).

Almost surely, 2^1961551691 is an apocalyptic number.

1961551691 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1961551691 is a deficient number, since it is larger than the sum of its proper divisors (273205813).

1961551691 is a wasteful number, since it uses less digits than its factorization.

1961551691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2195 (or 2184 counting only the distinct ones).

The product of its digits is 72900, while the sum is 44.

The square root of 1961551691 is about 44289.4083387891. The cubic root of 1961551691 is about 1251.7951148960.

The spelling of 1961551691 in words is "one billion, nine hundred sixty-one million, five hundred fifty-one thousand, six hundred ninety-one".