155405991 has 8 divisors (see below), whose sum is σ = 223147120. Its totient is φ = 95634432.

The previous prime is 155405989. The next prime is 155406001. The reversal of 155405991 is 199504551.

155405991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 155405991 - 2¹ = 155405989 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39), and also a Moran number because the ratio is a prime number: 3984769 = 155405991 / (1 + 5 + 5 + 4 + 0 + 5 + 9 + 9 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (155405951) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1992346 + ... + 1992423.

It is an arithmetic number, because the mean of its divisors is an integer number (27893390).

Almost surely, 2^155405991 is an apocalyptic number.

155405991 is a deficient number, since it is larger than the sum of its proper divisors (67741129).

155405991 is a wasteful number, since it uses less digits than its factorization.

155405991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3984785.

The product of its (nonzero) digits is 40500, while the sum is 39.

The square root of 155405991 is about 12466.1939259744. The cubic root of 155405991 is about 537.6371278755.

The spelling of 155405991 in words is "one hundred fifty-five million, four hundred five thousand, nine hundred ninety-one".