642166281 has 9 divisors (see below), whose sum is σ = 927683341. Its totient is φ = 428060172.

The previous prime is 642166249. The next prime is 642166303. The reversal of 642166281 is 182661246.

The square root of 642166281 is 25341.

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

642166281 is a `hidden beast` number, since 6 + 4 + 21 + 6 + 628 + 1 = 666.

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 642166281 - 2⁵ = 642166249 is a prime.

It is a super-2 number, since 2×642166281² = 824755064906741922, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (642166201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 71800 + ... + 80246.

Almost surely, 2^642166281 is an apocalyptic number.

642166281 is the 25341-st square number.

642166281 is the 12671-st centered octagonal number.

It is an amenable number.

642166281 is a deficient number, since it is larger than the sum of its proper divisors (285517060).

642166281 is an frugal number, since it uses more digits than its factorization.

642166281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16900 (or 8450 counting only the distinct ones).

The product of its digits is 27648, while the sum is 36.

The cubic root of 642166281 is about 862.7450958142.

Multiplying 642166281 by its sum of digits (36), we get a square (23117986116 = 152046²).

The spelling of 642166281 in words is "six hundred forty-two million, one hundred sixty-six thousand, two hundred eighty-one".