999664249861 has 2 divisors, whose sum is σ = 999664249862. Its totient is φ = 999664249860.

The previous prime is 999664249819. The next prime is 999664249867. The reversal of 999664249861 is 168942466999.

999664249861 = T₈₁₆₃₅₈ + T₈₁₆₃₅₉ + T₈₁₆₃₆₀.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 931331153025 + 68333096836 = 965055^2 + 261406^2 .

It is a cyclic number.

It is not a de Polignac number, because 999664249861 - 2⁷ = 999664249733 is a prime.

It is a super-2 number, since 2×999664249861² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (999664249867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499832124930 + 499832124931.

It is an arithmetic number, because the mean of its divisors is an integer number (499832124931).

Almost surely, 2^999664249861 is an apocalyptic number.

999664249861 is the 816360-th centered triangular number.

It is an amenable number.

999664249861 is a deficient number, since it is larger than the sum of its proper divisors (1).

999664249861 is an equidigital number, since it uses as much as digits as its factorization.

999664249861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 362797056, while the sum is 73.

The spelling of 999664249861 in words is "nine hundred ninety-nine billion, six hundred sixty-four million, two hundred forty-nine thousand, eight hundred sixty-one".