166521556 has 6 divisors (see below), whose sum is σ = 291412730. Its totient is φ = 83260776.

The previous prime is 166521533. The next prime is 166521617. The reversal of 166521556 is 655125661.

It can be written as a sum of positive squares in only one way, i.e., 166410000 + 111556 = 12900^2 + 334^2 .

It is a super-2 number, since 2×166521556² = 55458857225322272, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20815191 + ... + 20815198.

Almost surely, 2^166521556 is an apocalyptic number.

It is an amenable number.

166521556 is a deficient number, since it is larger than the sum of its proper divisors (124891174).

166521556 is a wasteful number, since it uses less digits than its factorization.

166521556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41630393 (or 41630391 counting only the distinct ones).

The product of its digits is 54000, while the sum is 37.

The square root of 166521556 is about 12904.3231515644. The cubic root of 166521556 is about 550.1614468192.

The spelling of 166521556 in words is "one hundred sixty-six million, five hundred twenty-one thousand, five hundred fifty-six".