66451961 has 2 divisors, whose sum is σ = 66451962. Its totient is φ = 66451960.

The previous prime is 66451951. The next prime is 66451967. The reversal of 66451961 is 16915466.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 63696361 + 2755600 = 7981^2 + 1660^2 .

It is a cyclic number.

It is not a de Polignac number, because 66451961 - 2¹⁸ = 66189817 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (66451967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33225980 + 33225981.

It is an arithmetic number, because the mean of its divisors is an integer number (33225981).

Almost surely, 2^66451961 is an apocalyptic number.

It is an amenable number.

66451961 is a deficient number, since it is larger than the sum of its proper divisors (1).

66451961 is an equidigital number, since it uses as much as digits as its factorization.

66451961 is an evil number, because the sum of its binary digits is even.

The product of its digits is 38880, while the sum is 38.

The square root of 66451961 is about 8151.8072229414. The cubic root of 66451961 is about 405.0443704880.

It can be divided in two parts, 664 and 51961, that added together give a palindrome (52625).

The spelling of 66451961 in words is "sixty-six million, four hundred fifty-one thousand, nine hundred sixty-one".