66938821 has 2 divisors, whose sum is σ = 66938822. Its totient is φ = 66938820.

The previous prime is 66938801. The next prime is 66938869. The reversal of 66938821 is 12883966.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 39753025 + 27185796 = 6305^2 + 5214^2 .

It is a cyclic number.

It is not a de Polignac number, because 66938821 - 2⁷ = 66938693 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66938801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33469410 + 33469411.

It is an arithmetic number, because the mean of its divisors is an integer number (33469411).

Almost surely, 2^66938821 is an apocalyptic number.

It is an amenable number.

66938821 is a deficient number, since it is larger than the sum of its proper divisors (1).

66938821 is an equidigital number, since it uses as much as digits as its factorization.

66938821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 124416, while the sum is 43.

The square root of 66938821 is about 8181.6148161595. The cubic root of 66938821 is about 406.0311497855.

The spelling of 66938821 in words is "sixty-six million, nine hundred thirty-eight thousand, eight hundred twenty-one".