155701991 has 4 divisors (see below), whose sum is σ = 155727000. Its totient is φ = 155676984.

The previous prime is 155701961. The next prime is 155701999. The reversal of 155701991 is 199107551.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 199107551 = 887 ⋅224473.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-155701991 is a prime.

It is a super-2 number, since 2×155701991² = 48486220002728162, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (155701999) 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, 5045 + ... + 18353.

It is an arithmetic number, because the mean of its divisors is an integer number (38931750).

Almost surely, 2^155701991 is an apocalyptic number.

155701991 is a deficient number, since it is larger than the sum of its proper divisors (25009).

155701991 is a wasteful number, since it uses less digits than its factorization.

155701991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25008.

The product of its (nonzero) digits is 14175, while the sum is 38.

The square root of 155701991 is about 12478.0603861337. The cubic root of 155701991 is about 537.9782551338.

The spelling of 155701991 in words is "one hundred fifty-five million, seven hundred one thousand, nine hundred ninety-one".