261919979819 has 2 divisors, whose sum is σ = 261919979820. Its totient is φ = 261919979818.

The previous prime is 261919979779. The next prime is 261919979903. The reversal of 261919979819 is 918979919162.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261919979819 is a prime.

It is a super-2 number, since 2×261919979819² (a number of 24 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (261919979719) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130959989909 + 130959989910.

It is an arithmetic number, because the mean of its divisors is an integer number (130959989910).

Almost surely, 2^261919979819 is an apocalyptic number.

261919979819 is a deficient number, since it is larger than the sum of its proper divisors (1).

261919979819 is an equidigital number, since it uses as much as digits as its factorization.

261919979819 is an evil number, because the sum of its binary digits is even.

The product of its digits is 39680928, while the sum is 71.

The spelling of 261919979819 in words is "two hundred sixty-one billion, nine hundred nineteen million, nine hundred seventy-nine thousand, eight hundred nineteen".