66999994 has 4 divisors (see below), whose sum is σ = 100499994. Its totient is φ = 33499996.

The previous prime is 66999983. The next prime is 66999997. The reversal of 66999994 is 49999966.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 49999966 = 2 ⋅24999983.

It can be written as a sum of positive squares in only one way, i.e., 35224225 + 31775769 = 5935^2 + 5637^2 .

It is not an unprimeable number, because it can be changed into a prime (66999997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 16749997 + ... + 16750000.

Almost surely, 2^66999994 is an apocalyptic number.

66999994 is a deficient number, since it is larger than the sum of its proper divisors (33500000).

66999994 is a wasteful number, since it uses less digits than its factorization.

66999994 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33499999.

The product of its digits is 8503056, while the sum is 61.

The square root of 66999994 is about 8185.3524053641. The cubic root of 66999994 is about 406.1547979205.

It can be divided in two parts, 6699 and 9994, that multiplied together give a triangular number (66949806 = T₁₁₅₇₁).

The spelling of 66999994 in words is "sixty-six million, nine hundred ninety-nine thousand, nine hundred ninety-four".