155802991 has 4 divisors (see below), whose sum is σ = 155854584. Its totient is φ = 155751400.

The previous prime is 155802973. The next prime is 155803001. The reversal of 155802991 is 199208551.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 199208551 = 43 ⋅4632757.

It is a cyclic number.

It is not a de Polignac number, because 155802991 - 2²⁵ = 122248559 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 (155802901) 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, 20965 + ... + 27406.

It is an arithmetic number, because the mean of its divisors is an integer number (38963646).

Almost surely, 2^155802991 is an apocalyptic number.

155802991 is a deficient number, since it is larger than the sum of its proper divisors (51593).

155802991 is an equidigital number, since it uses as much as digits as its factorization.

155802991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51592.

The product of its (nonzero) digits is 32400, while the sum is 40.

The square root of 155802991 is about 12482.1068333835. The cubic root of 155802991 is about 538.0945543515.

The spelling of 155802991 in words is "one hundred fifty-five million, eight hundred two thousand, nine hundred ninety-one".