1913216561 has 2 divisors, whose sum is σ = 1913216562. Its totient is φ = 1913216560.

The previous prime is 1913216537. The next prime is 1913216593. The reversal of 1913216561 is 1656123191.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1534680625 + 378535936 = 39175^2 + 19456^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1913216561 is a prime.

It is not a weakly prime, because it can be changed into another prime (1913216161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 956608280 + 956608281.

It is an arithmetic number, because the mean of its divisors is an integer number (956608281).

Almost surely, 2^1913216561 is an apocalyptic number.

It is an amenable number.

1913216561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1913216561 is an equidigital number, since it uses as much as digits as its factorization.

1913216561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9720, while the sum is 35.

The square root of 1913216561 is about 43740.3310572748. The cubic root of 1913216561 is about 1241.4275444774.

The spelling of 1913216561 in words is "one billion, nine hundred thirteen million, two hundred sixteen thousand, five hundred sixty-one".