66815947 has 4 divisors (see below), whose sum is σ = 72890136. Its totient is φ = 60741760.

The previous prime is 66815941. The next prime is 66815953. The reversal of 66815947 is 74951866.

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 (66815941) and next prime (66815953).

It is a cyclic number.

It is not a de Polignac number, because 66815947 - 2¹⁵ = 66783179 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 66815897 and 66815906.

It is not an unprimeable number, because it can be changed into a prime (66815941) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3037078 + ... + 3037099.

It is an arithmetic number, because the mean of its divisors is an integer number (18222534).

Almost surely, 2^66815947 is an apocalyptic number.

66815947 is a deficient number, since it is larger than the sum of its proper divisors (6074189).

66815947 is a wasteful number, since it uses less digits than its factorization.

66815947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6074188.

The product of its digits is 362880, while the sum is 46.

The square root of 66815947 is about 8174.1022136991. The cubic root of 66815947 is about 405.7825584667.

The spelling of 66815947 in words is "sixty-six million, eight hundred fifteen thousand, nine hundred forty-seven".