155559991 has 2 divisors, whose sum is σ = 155559992. Its totient is φ = 155559990.

The previous prime is 155559959. The next prime is 155560001. The reversal of 155559991 is 199955551.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 155559991 - 2⁵ = 155559959 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (155559941) 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 as a sum of consecutive naturals, namely, 77779995 + 77779996.

It is an arithmetic number, because the mean of its divisors is an integer number (77779996).

Almost surely, 2^155559991 is an apocalyptic number.

155559991 is a deficient number, since it is larger than the sum of its proper divisors (1).

155559991 is an equidigital number, since it uses as much as digits as its factorization.

155559991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 455625, while the sum is 49.

The square root of 155559991 is about 12472.3691013376. The cubic root of 155559991 is about 537.8146602499.

The spelling of 155559991 in words is "one hundred fifty-five million, five hundred fifty-nine thousand, nine hundred ninety-one".