642721471723 has 4 divisors (see below), whose sum is σ = 642723472120. Its totient is φ = 642719471328.

The previous prime is 642721471697. The next prime is 642721471727. The reversal of 642721471723 is 327174127246.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 327174127246 = 2 ⋅163587063623.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-642721471723 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (642721471727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 396990 + ... + 1201267.

It is an arithmetic number, because the mean of its divisors is an integer number (160680868030).

Almost surely, 2^642721471723 is an apocalyptic number.

642721471723 is a deficient number, since it is larger than the sum of its proper divisors (2000397).

642721471723 is a wasteful number, since it uses less digits than its factorization.

642721471723 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2000396.

The product of its digits is 790272, while the sum is 46.

Adding to 642721471723 its reverse (327174127246), we get a palindrome (969895598969).

The spelling of 642721471723 in words is "six hundred forty-two billion, seven hundred twenty-one million, four hundred seventy-one thousand, seven hundred twenty-three".