66399951 has 8 divisors (see below), whose sum is σ = 90692784. Its totient is φ = 43186880.

The previous prime is 66399929. The next prime is 66399961. The reversal of 66399951 is 15999366.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 66399951 - 2¹⁷ = 66268879 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 66399951.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66399901) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 269796 + ... + 270041.

It is an arithmetic number, because the mean of its divisors is an integer number (11336598).

Almost surely, 2^66399951 is an apocalyptic number.

66399951 is a deficient number, since it is larger than the sum of its proper divisors (24292833).

66399951 is a wasteful number, since it uses less digits than its factorization.

66399951 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 539881.

The product of its digits is 393660, while the sum is 48.

The square root of 66399951 is about 8148.6165083405. The cubic root of 66399951 is about 404.9386707926.

The spelling of 66399951 in words is "sixty-six million, three hundred ninety-nine thousand, nine hundred fifty-one".