51643666 has 4 divisors (see below), whose sum is σ = 77465502. Its totient is φ = 25821832.

The previous prime is 51643651. The next prime is 51643681. The reversal of 51643666 is 66634615.

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

It is an interprime number because it is at equal distance from previous prime (51643651) and next prime (51643681).

It can be written as a sum of positive squares in only one way, i.e., 51538041 + 105625 = 7179^2 + 325^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12910915 + ... + 12910918.

Almost surely, 2^51643666 is an apocalyptic number.

51643666 is a deficient number, since it is larger than the sum of its proper divisors (25821836).

51643666 is a wasteful number, since it uses less digits than its factorization.

51643666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25821835.

The product of its digits is 77760, while the sum is 37.

The square root of 51643666 is about 7186.3527606151. The cubic root of 51643666 is about 372.3965834559.

The spelling of 51643666 in words is "fifty-one million, six hundred forty-three thousand, six hundred sixty-six".