156109991 has 4 divisors (see below), whose sum is σ = 157143984. Its totient is φ = 155076000.

The previous prime is 156109973. The next prime is 156110021. The reversal of 156109991 is 199901651.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-156109991 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (156109951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 516770 + ... + 517071.

It is an arithmetic number, because the mean of its divisors is an integer number (39285996).

Almost surely, 2^156109991 is an apocalyptic number.

156109991 is a deficient number, since it is larger than the sum of its proper divisors (1033993).

156109991 is a wasteful number, since it uses less digits than its factorization.

156109991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1033992.

The product of its (nonzero) digits is 21870, while the sum is 41.

The square root of 156109991 is about 12494.3983848763. The cubic root of 156109991 is about 538.4477496349.

The spelling of 156109991 in words is "one hundred fifty-six million, one hundred nine thousand, nine hundred ninety-one".