261919979851 has 4 divisors (see below), whose sum is σ = 261998803512. Its totient is φ = 261841156192.

The previous prime is 261919979819. The next prime is 261919979903. The reversal of 261919979851 is 158979919162.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 261919979851 - 2⁵ = 261919979819 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261919979351) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39406846 + ... + 39413491.

It is an arithmetic number, because the mean of its divisors is an integer number (65499700878).

Almost surely, 2^261919979851 is an apocalyptic number.

261919979851 is a deficient number, since it is larger than the sum of its proper divisors (78823661).

261919979851 is an equidigital number, since it uses as much as digits as its factorization.

261919979851 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78823660.

The product of its digits is 22044960, while the sum is 67.

The spelling of 261919979851 in words is "two hundred sixty-one billion, nine hundred nineteen million, nine hundred seventy-nine thousand, eight hundred fifty-one".