1661517397 has 2 divisors, whose sum is σ = 1661517398. Its totient is φ = 1661517396.

The previous prime is 1661517379. The next prime is 1661517413. The reversal of 1661517397 is 7937151661.

Together with previous prime (1661517379) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1420460721 + 241056676 = 37689^2 + 15526^2 .

It is an emirp because it is prime and its reverse (7937151661) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1661517397 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1661517317) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830758698 + 830758699.

It is an arithmetic number, because the mean of its divisors is an integer number (830758699).

Almost surely, 2^1661517397 is an apocalyptic number.

It is an amenable number.

1661517397 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661517397 is an equidigital number, since it uses as much as digits as its factorization.

1661517397 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 238140, while the sum is 46.

The square root of 1661517397 is about 40761.7148437109. The cubic root of 1661517397 is about 1184.4088150012.

The spelling of 1661517397 in words is "one billion, six hundred sixty-one million, five hundred seventeen thousand, three hundred ninety-seven".