1951661591 has 16 divisors (see below), whose sum is σ = 2265055488. Its totient is φ = 1661923200.

The previous prime is 1951661587. The next prime is 1951661603.

1951661591 is nontrivially palindromic in base 10.

It is a cyclic number.

It is not a de Polignac number, because 1951661591 - 2² = 1951661587 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1951661501) 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 15 ways as a sum of consecutive naturals, for example, 14726 + ... + 64188.

It is an arithmetic number, because the mean of its divisors is an integer number (141565968).

Almost surely, 2^1951661591 is an apocalyptic number.

1951661591 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1951661591 is a deficient number, since it is larger than the sum of its proper divisors (313393897).

1951661591 is a wasteful number, since it uses less digits than its factorization.

1951661591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49702.

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

The square root of 1951661591 is about 44177.6141388373. The cubic root of 1951661591 is about 1249.6877280755.

The spelling of 1951661591 in words is "one billion, nine hundred fifty-one million, six hundred sixty-one thousand, five hundred ninety-one".