66019781 has 4 divisors (see below), whose sum is σ = 66293964. Its totient is φ = 65745600.

The previous prime is 66019771. The next prime is 66019817. The reversal of 66019781 is 18791066.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 57988225 + 8031556 = 7615^2 + 2834^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66019781 is a prime.

It is a super-2 number, since 2×66019781² = 8717222966575922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66019711) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136730 + ... + 137211.

It is an arithmetic number, because the mean of its divisors is an integer number (16573491).

Almost surely, 2^66019781 is an apocalyptic number.

It is an amenable number.

66019781 is a deficient number, since it is larger than the sum of its proper divisors (274183).

66019781 is a wasteful number, since it uses less digits than its factorization.

66019781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 274182.

The product of its (nonzero) digits is 18144, while the sum is 38.

The square root of 66019781 is about 8125.2557498210. The cubic root of 66019781 is about 404.1643716500.

The spelling of 66019781 in words is "sixty-six million, nineteen thousand, seven hundred eighty-one".