618991991 has 2 divisors, whose sum is σ = 618991992. Its totient is φ = 618991990.

The previous prime is 618991963. The next prime is 618992053. The reversal of 618991991 is 199199816.

618991991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 618991991 - 2¹⁴ = 618975607 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (618991931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 309495995 + 309495996.

It is an arithmetic number, because the mean of its divisors is an integer number (309495996).

Almost surely, 2^618991991 is an apocalyptic number.

618991991 is a deficient number, since it is larger than the sum of its proper divisors (1).

618991991 is an equidigital number, since it uses as much as digits as its factorization.

618991991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 314928, while the sum is 53.

The square root of 618991991 is about 24879.5496542843. The cubic root of 618991991 is about 852.2395341219.

The spelling of 618991991 in words is "six hundred eighteen million, nine hundred ninety-one thousand, nine hundred ninety-one".