139666 has 4 divisors (see below), whose sum is σ = 209502. Its totient is φ = 69832.

The previous prime is 139663. The next prime is 139681. The reversal of 139666 is 666931.

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

It can be written as a sum of positive squares in only one way, i.e., 137641 + 2025 = 371^2 + 45^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a plaindrome in base 12.

It is not an unprimeable number, because it can be changed into a prime (139661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 34915 + ... + 34918.

2¹³⁹⁶⁶⁶ is an apocalyptic number.

139666 is a deficient number, since it is larger than the sum of its proper divisors (69836).

139666 is an equidigital number, since it uses as much as digits as its factorization.

139666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69835.

The product of its digits is 5832, while the sum is 31.

The square root of 139666 is about 373.7191458836. The cubic root of 139666 is about 51.8836154462.

The spelling of 139666 in words is "one hundred thirty-nine thousand, six hundred sixty-six".