61971658561 has 2 divisors, whose sum is σ = 61971658562. Its totient is φ = 61971658560.

The previous prime is 61971658537. The next prime is 61971658571. The reversal of 61971658561 is 16585617916.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 51535810225 + 10435848336 = 227015^2 + 102156^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-61971658561 is a prime.

It is not a weakly prime, because it can be changed into another prime (61971658571) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30985829280 + 30985829281.

It is an arithmetic number, because the mean of its divisors is an integer number (30985829281).

Almost surely, 2^61971658561 is an apocalyptic number.

It is an amenable number.

61971658561 is a deficient number, since it is larger than the sum of its proper divisors (1).

61971658561 is an equidigital number, since it uses as much as digits as its factorization.

61971658561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2721600, while the sum is 55.

The spelling of 61971658561 in words is "sixty-one billion, nine hundred seventy-one million, six hundred fifty-eight thousand, five hundred sixty-one".