1678615991 has 6 divisors (see below), whose sum is σ = 1817673120. Its totient is φ = 1549491528.

The previous prime is 1678615949. The next prime is 1678616033. The reversal of 1678615991 is 1995168761.

It is an interprime number because it is at equal distance from previous prime (1678615949) and next prime (1678616033).

It is not a de Polignac number, because 1678615991 - 2²² = 1674421687 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 (1678615391) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4966151 + ... + 4966488.

It is an arithmetic number, because the mean of its divisors is an integer number (302945520).

Almost surely, 2^1678615991 is an apocalyptic number.

1678615991 is a deficient number, since it is larger than the sum of its proper divisors (139057129).

1678615991 is an equidigital number, since it uses as much as digits as its factorization.

1678615991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9932665 (or 9932652 counting only the distinct ones).

The product of its digits is 816480, while the sum is 53.

The square root of 1678615991 is about 40970.9164042007. The cubic root of 1678615991 is about 1188.4578547775.

The spelling of 1678615991 in words is "one billion, six hundred seventy-eight million, six hundred fifteen thousand, nine hundred ninety-one".