61691957729 has 4 divisors (see below), whose sum is σ = 61714369476. Its totient is φ = 61669545984.

The previous prime is 61691957711. The next prime is 61691957731. The reversal of 61691957729 is 92775919616.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 57205637329 + 4486320400 = 239177^2 + 66980^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-61691957729 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (61691957779) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11201744 + ... + 11207249.

It is an arithmetic number, because the mean of its divisors is an integer number (15428592369).

Almost surely, 2^61691957729 is an apocalyptic number.

It is an amenable number.

61691957729 is a deficient number, since it is larger than the sum of its proper divisors (22411747).

61691957729 is a wasteful number, since it uses less digits than its factorization.

61691957729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22411746.

The product of its digits is 12859560, while the sum is 62.

The spelling of 61691957729 in words is "sixty-one billion, six hundred ninety-one million, nine hundred fifty-seven thousand, seven hundred twenty-nine".