66691481 has 2 divisors, whose sum is σ = 66691482. Its totient is φ = 66691480.

The previous prime is 66691451. The next prime is 66691511. The reversal of 66691481 is 18419666.

It is a balanced prime because it is at equal distance from previous prime (66691451) and next prime (66691511).

It can be written as a sum of positive squares in only one way, i.e., 64080025 + 2611456 = 8005^2 + 1616^2 .

It is a cyclic number.

It is not a de Polignac number, because 66691481 - 2¹⁴ = 66675097 is a prime.

It is a super-2 number, since 2×66691481² = 8895507275946722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (66691451) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33345740 + 33345741.

It is an arithmetic number, because the mean of its divisors is an integer number (33345741).

Almost surely, 2^66691481 is an apocalyptic number.

It is an amenable number.

66691481 is a deficient number, since it is larger than the sum of its proper divisors (1).

66691481 is an equidigital number, since it uses as much as digits as its factorization.

66691481 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 62208, while the sum is 41.

The square root of 66691481 is about 8166.4852292770. The cubic root of 66691481 is about 405.5304353936.

It can be divided in two parts, 6669 and 1481, that multiplied together give a palindrome (9876789).

The spelling of 66691481 in words is "sixty-six million, six hundred ninety-one thousand, four hundred eighty-one".