1961615991 has 8 divisors (see below), whose sum is σ = 2616000640. Its totient is φ = 1307487672.

The previous prime is 1961615987. The next prime is 1961616001. The reversal of 1961615991 is 1995161691.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1961615991 - 2² = 1961615987 is a prime.

It is a super-2 number, since 2×1961615991² = 7695874592293824162, which contains 22 as substring.

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 1961615991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1961615911) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 45451 + ... + 77388.

It is an arithmetic number, because the mean of its divisors is an integer number (327000080).

Almost surely, 2^1961615991 is an apocalyptic number.

1961615991 is a deficient number, since it is larger than the sum of its proper divisors (654384649).

1961615991 is a wasteful number, since it uses less digits than its factorization.

1961615991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128165.

The product of its digits is 131220, while the sum is 48.

The square root of 1961615991 is about 44290.1342400314. The cubic root of 1961615991 is about 1251.8087927658.

The spelling of 1961615991 in words is "one billion, nine hundred sixty-one million, six hundred fifteen thousand, nine hundred ninety-one".