78257213561 has 2 divisors, whose sum is σ = 78257213562. Its totient is φ = 78257213560.

The previous prime is 78257213543. The next prime is 78257213563. The reversal of 78257213561 is 16531275287.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 77767919161 + 489294400 = 278869^2 + 22120^2 .

It is an emirp because it is prime and its reverse (16531275287) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78257213561 - 2⁶ = 78257213497 is a prime.

It is a super-2 number, since 2×78257213561² (a number of 23 digits) contains 22 as substring.

It is a Sophie Germain prime.

Together with 78257213563, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (78257213563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39128606780 + 39128606781.

It is an arithmetic number, because the mean of its divisors is an integer number (39128606781).

Almost surely, 2^78257213561 is an apocalyptic number.

It is an amenable number.

78257213561 is a deficient number, since it is larger than the sum of its proper divisors (1).

78257213561 is an equidigital number, since it uses as much as digits as its factorization.

78257213561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 705600, while the sum is 47.

The spelling of 78257213561 in words is "seventy-eight billion, two hundred fifty-seven million, two hundred thirteen thousand, five hundred sixty-one".