1971561779 has 6 divisors (see below), whose sum is σ = 2167088700. Its totient is φ = 1792328780.

The previous prime is 1971561749. The next prime is 1971561853. The reversal of 1971561779 is 9771651791.

It is not a de Polignac number, because 1971561779 - 2²⁰ = 1970513203 is a prime.

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 1971561779.

It is not an unprimeable number, because it can be changed into a prime (1971561749) 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, 8146829 + ... + 8147070.

It is an arithmetic number, because the mean of its divisors is an integer number (361181450).

Almost surely, 2^1971561779 is an apocalyptic number.

1971561779 is a deficient number, since it is larger than the sum of its proper divisors (195526921).

1971561779 is a wasteful number, since it uses less digits than its factorization.

1971561779 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16293921 (or 16293910 counting only the distinct ones).

The product of its digits is 833490, while the sum is 53.

The square root of 1971561779 is about 44402.2722278939. The cubic root of 1971561779 is about 1253.9208680958.

The spelling of 1971561779 in words is "one billion, nine hundred seventy-one million, five hundred sixty-one thousand, seven hundred seventy-nine".