61635708721 has 4 divisors (see below), whose sum is σ = 62480033572. Its totient is φ = 60791383872.

The previous prime is 61635708713. The next prime is 61635708737. The reversal of 61635708721 is 12780753616.

61635708721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 27015524496 + 34620184225 = 164364^2 + 186065^2 .

It is a cyclic number.

It is not a de Polignac number, because 61635708721 - 2³ = 61635708713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (61635708781) 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, 422162316 + ... + 422162461.

It is an arithmetic number, because the mean of its divisors is an integer number (15620008393).

Almost surely, 2^61635708721 is an apocalyptic number.

It is an amenable number.

61635708721 is a deficient number, since it is larger than the sum of its proper divisors (844324851).

61635708721 is an equidigital number, since it uses as much as digits as its factorization.

61635708721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 844324850.

The product of its (nonzero) digits is 423360, while the sum is 46.

The spelling of 61635708721 in words is "sixty-one billion, six hundred thirty-five million, seven hundred eight thousand, seven hundred twenty-one".