1291749961 has 2 divisors, whose sum is σ = 1291749962. Its totient is φ = 1291749960.

The previous prime is 1291749959. The next prime is 1291749967. The reversal of 1291749961 is 1699471921.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 747694336 + 544055625 = 27344^2 + 23325^2 .

It is a cyclic number.

It is not a de Polignac number, because 1291749961 - 2¹ = 1291749959 is a prime.

Together with 1291749959, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (1291749967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 645874980 + 645874981.

It is an arithmetic number, because the mean of its divisors is an integer number (645874981).

Almost surely, 2^1291749961 is an apocalyptic number.

It is an amenable number.

1291749961 is a deficient number, since it is larger than the sum of its proper divisors (1).

1291749961 is an equidigital number, since it uses as much as digits as its factorization.

1291749961 is an evil number, because the sum of its binary digits is even.

The product of its digits is 244944, while the sum is 49.

The square root of 1291749961 is about 35940.9232073969. The cubic root of 1291749961 is about 1089.0792552731.

The spelling of 1291749961 in words is "one billion, two hundred ninety-one million, seven hundred forty-nine thousand, nine hundred sixty-one".