155861209 has 6 divisors (see below), whose sum is σ = 181307994. Its totient is φ = 133595280.

The previous prime is 155861159. The next prime is 155861227. The reversal of 155861209 is 902168551.

It can be written as a sum of positive squares in only one way, i.e., 82810000 + 73051209 = 9100^2 + 8547^2 .

It is not a de Polignac number, because 155861209 - 2¹⁹ = 155336921 is a prime.

It is not an unprimeable number, because it can be changed into a prime (155861509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1590372 + ... + 1590469.

It is an arithmetic number, because the mean of its divisors is an integer number (30217999).

Almost surely, 2^155861209 is an apocalyptic number.

It is an amenable number.

155861209 is a deficient number, since it is larger than the sum of its proper divisors (25446785).

155861209 is an equidigital number, since it uses as much as digits as its factorization.

155861209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3180855 (or 3180848 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 37.

The square root of 155861209 is about 12484.4386738051. The cubic root of 155861209 is about 538.1615682290.

The spelling of 155861209 in words is "one hundred fifty-five million, eight hundred sixty-one thousand, two hundred nine".