155221666 has 4 divisors (see below), whose sum is σ = 232832502. Its totient is φ = 77610832.

The previous prime is 155221639. The next prime is 155221673. The reversal of 155221666 is 666122551.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 151905625 + 3316041 = 12325^2 + 1821^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38805415 + ... + 38805418.

Almost surely, 2^155221666 is an apocalyptic number.

155221666 is a deficient number, since it is larger than the sum of its proper divisors (77610836).

155221666 is an equidigital number, since it uses as much as digits as its factorization.

155221666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77610835.

The product of its digits is 21600, while the sum is 34.

The square root of 155221666 is about 12458.7987382412. The cubic root of 155221666 is about 537.4244823416.

The spelling of 155221666 in words is "one hundred fifty-five million, two hundred twenty-one thousand, six hundred sixty-six".