191220139 has 4 divisors (see below), whose sum is σ = 208603800. Its totient is φ = 173836480.

The previous prime is 191220119. The next prime is 191220143. The reversal of 191220139 is 931022191.

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

It is a cyclic number.

It is not a de Polignac number, because 191220139 - 2¹³ = 191211947 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (191220109) 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, 8691814 + ... + 8691835.

It is an arithmetic number, because the mean of its divisors is an integer number (52150950).

Almost surely, 2^191220139 is an apocalyptic number.

191220139 is a deficient number, since it is larger than the sum of its proper divisors (17383661).

191220139 is a wasteful number, since it uses less digits than its factorization.

191220139 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17383660.

The product of its (nonzero) digits is 972, while the sum is 28.

The square root of 191220139 is about 13828.2370170604. The cubic root of 191220139 is about 576.1176889070.

The spelling of 191220139 in words is "one hundred ninety-one million, two hundred twenty thousand, one hundred thirty-nine".