642166021 has 12 divisors (see below), whose sum is σ = 747633888. Its totient is φ = 549967992.

The previous prime is 642166001. The next prime is 642166039. The reversal of 642166021 is 120661246.

It is not a de Polignac number, because 642166021 - 2⁷ = 642165893 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (642166001) 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 11 ways as a sum of consecutive naturals, for example, 62190 + ... + 71776.

It is an arithmetic number, because the mean of its divisors is an integer number (62302824).

Almost surely, 2^642166021 is an apocalyptic number.

It is an amenable number.

642166021 is a deficient number, since it is larger than the sum of its proper divisors (105467867).

642166021 is a wasteful number, since it uses less digits than its factorization.

642166021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10968 (or 10961 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 642166021 is about 25340.9948699730. The cubic root of 642166021 is about 862.7449793782.

The spelling of 642166021 in words is "six hundred forty-two million, one hundred sixty-six thousand, twenty-one".