61891535861 has 2 divisors, whose sum is σ = 61891535862. Its totient is φ = 61891535860.

The previous prime is 61891535837. The next prime is 61891535863. The reversal of 61891535861 is 16853519816.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 56693991025 + 5197544836 = 238105^2 + 72094^2 .

It is a cyclic number.

It is not a de Polignac number, because 61891535861 - 2¹⁴ = 61891519477 is a prime.

It is a super-2 number, since 2×61891535861² (a number of 22 digits) contains 22 as substring.

It is a Sophie Germain prime.

Together with 61891535863, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (61891535863) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30945767930 + 30945767931.

It is an arithmetic number, because the mean of its divisors is an integer number (30945767931).

Almost surely, 2^61891535861 is an apocalyptic number.

It is an amenable number.

61891535861 is a deficient number, since it is larger than the sum of its proper divisors (1).

61891535861 is an equidigital number, since it uses as much as digits as its factorization.

61891535861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1555200, while the sum is 53.

The spelling of 61891535861 in words is "sixty-one billion, eight hundred ninety-one million, five hundred thirty-five thousand, eight hundred sixty-one".