166503986401 has 3 divisors (see below), whose sum is σ = 166504394451. Its totient is φ = 166503578352.

The previous prime is 166503986377. The next prime is 166503986449. The reversal of 166503986401 is 104689305661.

The square root of 166503986401 is 408049.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 139278986401 + 27225000000 = 373201^2 + 165000^2 .

It is not a de Polignac number, because 166503986401 - 2¹⁵ = 166503953633 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (166503986801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 204025 + ... + 612073.

It is an arithmetic number, because the mean of its divisors is an integer number (55501464817).

Almost surely, 2^166503986401 is an apocalyptic number.

166503986401 is the 408049-th square number.

166503986401 is the 204025-th centered octagonal number.

It is an amenable number.

166503986401 is a deficient number, since it is larger than the sum of its proper divisors (408050).

166503986401 is an frugal number, since it uses more digits than its factorization.

166503986401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 816098 (or 408049 counting only the distinct ones).

The product of its (nonzero) digits is 933120, while the sum is 49.

Multiplying 166503986401 by its sum of digits (49), we get a square (8158695333649 = 2856343²).

The spelling of 166503986401 in words is "one hundred sixty-six billion, five hundred three million, nine hundred eighty-six thousand, four hundred one".