642999721 has 16 divisors (see below), whose sum is σ = 837938304. Its totient is φ = 478819584.

The previous prime is 642999713. The next prime is 642999733. The reversal of 642999721 is 127999246.

642999721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 642999721 - 2³ = 642999713 is a prime.

It is not an unprimeable number, because it can be changed into a prime (642999421) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 206275 + ... + 209368.

It is an arithmetic number, because the mean of its divisors is an integer number (52371144).

Almost surely, 2^642999721 is an apocalyptic number.

It is an amenable number.

642999721 is a deficient number, since it is larger than the sum of its proper divisors (194938583).

642999721 is a wasteful number, since it uses less digits than its factorization.

642999721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 415680.

The product of its digits is 489888, while the sum is 49.

The square root of 642999721 is about 25357.4391648684. The cubic root of 642999721 is about 863.1181743791.

The spelling of 642999721 in words is "six hundred forty-two million, nine hundred ninety-nine thousand, seven hundred twenty-one".