66811491 has 6 divisors (see below), whose sum is σ = 96505500. Its totient is φ = 44540988.

The previous prime is 66811471. The next prime is 66811517. The reversal of 66811491 is 19411866.

It is a happy number.

It is not a de Polignac number, because 66811491 - 2¹⁰ = 66810467 is a prime.

It is not an unprimeable number, because it can be changed into a prime (66811421) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3711741 + ... + 3711758.

It is an arithmetic number, because the mean of its divisors is an integer number (16084250).

Almost surely, 2^66811491 is an apocalyptic number.

66811491 is a deficient number, since it is larger than the sum of its proper divisors (29694009).

66811491 is a wasteful number, since it uses less digits than its factorization.

66811491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7423505 (or 7423502 counting only the distinct ones).

The product of its digits is 10368, while the sum is 36.

The square root of 66811491 is about 8173.8296409945. The cubic root of 66811491 is about 405.7735376298.

The spelling of 66811491 in words is "sixty-six million, eight hundred eleven thousand, four hundred ninety-one".