61721744681 has 2 divisors, whose sum is σ = 61721744682. Its totient is φ = 61721744680.

The previous prime is 61721744677. The next prime is 61721744699. The reversal of 61721744681 is 18644712716.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 36198487081 + 25523257600 = 190259^2 + 159760^2 .

It is a cyclic number.

It is not a de Polignac number, because 61721744681 - 2² = 61721744677 is a prime.

It is a super-2 number, since 2×61721744681² (a number of 22 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (61721744641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30860872340 + 30860872341.

It is an arithmetic number, because the mean of its divisors is an integer number (30860872341).

Almost surely, 2^61721744681 is an apocalyptic number.

It is an amenable number.

61721744681 is a deficient number, since it is larger than the sum of its proper divisors (1).

61721744681 is an equidigital number, since it uses as much as digits as its factorization.

61721744681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 451584, while the sum is 47.

The spelling of 61721744681 in words is "sixty-one billion, seven hundred twenty-one million, seven hundred forty-four thousand, six hundred eighty-one".