642221163781 has 2 divisors, whose sum is σ = 642221163782. Its totient is φ = 642221163780.

The previous prime is 642221163769. The next prime is 642221163791. The reversal of 642221163781 is 187361122246.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 618692364900 + 23528798881 = 786570^2 + 153391^2 .

It is a cyclic number.

It is not a de Polignac number, because 642221163781 - 2¹⁷ = 642221032709 is a prime.

It is a super-2 number, since 2×642221163781² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (642221163751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321110581890 + 321110581891.

It is an arithmetic number, because the mean of its divisors is an integer number (321110581891).

Almost surely, 2^642221163781 is an apocalyptic number.

It is an amenable number.

642221163781 is a deficient number, since it is larger than the sum of its proper divisors (1).

642221163781 is an equidigital number, since it uses as much as digits as its factorization.

642221163781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 193536, while the sum is 43.

The spelling of 642221163781 in words is "six hundred forty-two billion, two hundred twenty-one million, one hundred sixty-three thousand, seven hundred eighty-one".