66166421 has 2 divisors, whose sum is σ = 66166422. Its totient is φ = 66166420.

The previous prime is 66166409. The next prime is 66166439. The reversal of 66166421 is 12466166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 63377521 + 2788900 = 7961^2 + 1670^2 .

It is a cyclic number.

It is not a de Polignac number, because 66166421 - 2¹⁴ = 66150037 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66166021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33083210 + 33083211.

It is an arithmetic number, because the mean of its divisors is an integer number (33083211).

Almost surely, 2^66166421 is an apocalyptic number.

It is an amenable number.

66166421 is a deficient number, since it is larger than the sum of its proper divisors (1).

66166421 is an equidigital number, since it uses as much as digits as its factorization.

66166421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10368, while the sum is 32.

The square root of 66166421 is about 8134.2744605773. The cubic root of 66166421 is about 404.4633872710.

The spelling of 66166421 in words is "sixty-six million, one hundred sixty-six thousand, four hundred twenty-one".