7811520007661 has 2 divisors, whose sum is σ = 7811520007662. Its totient is φ = 7811520007660.

The previous prime is 7811520007649. The next prime is 7811520007667. The reversal of 7811520007661 is 1667000251187.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 4905538374025 + 2905981633636 = 2214845^2 + 1704694^2 .

It is an emirp because it is prime and its reverse (1667000251187) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 7811520007661 - 2¹⁴ = 7811519991277 is a prime.

It is a super-2 number, since 2×7811520007661² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7811520007667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3905760003830 + 3905760003831.

It is an arithmetic number, because the mean of its divisors is an integer number (3905760003831).

Almost surely, 2^{7811520007661} is an apocalyptic number.

It is an amenable number.

7811520007661 is a deficient number, since it is larger than the sum of its proper divisors (1).

7811520007661 is an equidigital number, since it uses as much as digits as its factorization.

7811520007661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 141120, while the sum is 44.

The spelling of 7811520007661 in words is "seven trillion, eight hundred eleven billion, five hundred twenty million, seven thousand, six hundred sixty-one".