156697991 has 4 divisors (see below), whose sum is σ = 162101400. Its totient is φ = 151294584.

The previous prime is 156697951. The next prime is 156698021. The reversal of 156697991 is 199796651.

It is a happy number.

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 156697991 - 2¹⁴ = 156681607 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 (156697951) 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, 2701661 + ... + 2701718.

It is an arithmetic number, because the mean of its divisors is an integer number (40525350).

Almost surely, 2^156697991 is an apocalyptic number.

156697991 is a deficient number, since it is larger than the sum of its proper divisors (5403409).

156697991 is an equidigital number, since it uses as much as digits as its factorization.

156697991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5403408.

The product of its digits is 918540, while the sum is 53.

The square root of 156697991 is about 12517.9068138407. The cubic root of 156697991 is about 539.1229372512.

The spelling of 156697991 in words is "one hundred fifty-six million, six hundred ninety-seven thousand, nine hundred ninety-one".