664571191961 has 2 divisors, whose sum is σ = 664571191962. Its totient is φ = 664571191960.

The previous prime is 664571191903. The next prime is 664571191967. The reversal of 664571191961 is 169191175466.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 586995016336 + 77576175625 = 766156^2 + 278525^2 .

It is a cyclic number.

It is not a de Polignac number, because 664571191961 - 2¹⁴ = 664571175577 is a prime.

It is a super-3 number, since 3×664571191961³ (a number of 36 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a junction number, because it is equal to n+sod(n) for n = 664571191897 and 664571191906.

It is not a weakly prime, because it can be changed into another prime (664571191967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332285595980 + 332285595981.

It is an arithmetic number, because the mean of its divisors is an integer number (332285595981).

Almost surely, 2^664571191961 is an apocalyptic number.

It is an amenable number.

664571191961 is a deficient number, since it is larger than the sum of its proper divisors (1).

664571191961 is an equidigital number, since it uses as much as digits as its factorization.

664571191961 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2449440, while the sum is 56.

The spelling of 664571191961 in words is "six hundred sixty-four billion, five hundred seventy-one million, one hundred ninety-one thousand, nine hundred sixty-one".