155665661 has 2 divisors, whose sum is σ = 155665662.
Its totient is φ = 155665660.
The previous prime is 155665639. The next prime is 155665667. The reversal of 155665661 is 166566551.
It is a strong prime.
It can be written as a sum of positive squares in only one way, i.e., 112763161 + 42902500 = 10619^2 + 6550^2
It is a cyclic number.
It is not a de Polignac number, because 155665661 - 210 = 155664637 is a prime.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (155665667) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 77832830 + 77832831.
It is an arithmetic number, because the mean of its divisors is an integer number (77832831).
Almost surely, 2155665661 is an apocalyptic number.
It is an amenable number.
155665661 is a deficient number, since it is larger than the sum of its proper divisors (1).
155665661 is an equidigital number, since it uses as much as digits as its factorization.
155665661 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 162000, while the sum is 41.
The square root of 155665661 is about 12476.6045461095.
The cubic root of 155665661 is about 537.9364096609.
The spelling of 155665661 in words is "one hundred fifty-five million, six hundred sixty-five thousand, six hundred sixty-one".