66786021983521 has 16 divisors (see below), whose sum is σ = 68329020389760. Its totient is φ = 65259806698240.

The previous prime is 66786021983459. The next prime is 66786021983557. The reversal of 66786021983521 is 12538912068766.

It is a cyclic number.

It is not a de Polignac number, because 66786021983521 - 2²³ = 66786013594913 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66786021993521) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 195695010 + ... + 196035988.

It is an arithmetic number, because the mean of its divisors is an integer number (4270563774360).

Almost surely, 2^{66786021983521} is an apocalyptic number.

It is an amenable number.

66786021983521 is a deficient number, since it is larger than the sum of its proper divisors (1542998406239).

66786021983521 is a wasteful number, since it uses less digits than its factorization.

66786021983521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 365576.

The product of its (nonzero) digits is 52254720, while the sum is 64.

The spelling of 66786021983521 in words is "sixty-six trillion, seven hundred eighty-six billion, twenty-one million, nine hundred eighty-three thousand, five hundred twenty-one".