19651256761 has 2 divisors, whose sum is σ = 19651256762. Its totient is φ = 19651256760.

The previous prime is 19651256759. The next prime is 19651256773. The reversal of 19651256761 is 16765215691.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18693725625 + 957531136 = 136725^2 + 30944^2 .

It is a cyclic number.

It is not a de Polignac number, because 19651256761 - 2¹ = 19651256759 is a prime.

It is a super-2 number, since 2×19651256761² (a number of 21 digits) contains 22 as substring.

Together with 19651256759, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (19651256701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9825628380 + 9825628381.

It is an arithmetic number, because the mean of its divisors is an integer number (9825628381).

Almost surely, 2^19651256761 is an apocalyptic number.

It is an amenable number.

19651256761 is a deficient number, since it is larger than the sum of its proper divisors (1).

19651256761 is an equidigital number, since it uses as much as digits as its factorization.

19651256761 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 680400, while the sum is 49.

The spelling of 19651256761 in words is "nineteen billion, six hundred fifty-one million, two hundred fifty-six thousand, seven hundred sixty-one".