66890921043969 has 45 divisors (see below), whose sum is σ = 109834570233619. Its totient is φ = 40539461426640.

The previous prime is 66890921043911. The next prime is 66890921043979. The reversal of 66890921043969 is 96934012909866.

The square root of 66890921043969 is 8178687.

It is a perfect power (a square), and thus also a powerful number.

66890921043969 is a `hidden beast` number, since 6 + 6 + 8 + 90 + 92 + 10 + 439 + 6 + 9 = 666.

It can be written as a sum of positive squares in only one way, i.e., 50744893367025 + 16146027676944 = 7123545^2 + 4018212^2 .

It is not a de Polignac number, because 66890921043969 - 2¹⁷ = 66890920912897 is a prime.

It is a super-2 number, since 2×66890921043969² (a number of 28 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 66890921043897 and 66890921043906.

It is not an unprimeable number, because it can be changed into a prime (66890921043979) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 809648707 + ... + 809731319.

Almost surely, 2^{66890921043969} is an apocalyptic number.

66890921043969 is the 8178687-th square number.

66890921043969 is the 4089344-th centered octagonal number.

It is an amenable number.

66890921043969 is a deficient number, since it is larger than the sum of its proper divisors (42943649189650).

66890921043969 is an frugal number, since it uses more digits than its factorization.

66890921043969 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165260 (or 82627 counting only the distinct ones).

The product of its (nonzero) digits is 272097792, while the sum is 72.

The spelling of 66890921043969 in words is "sixty-six trillion, eight hundred ninety billion, nine hundred twenty-one million, forty-three thousand, nine hundred sixty-nine".