642906881 has 4 divisors (see below), whose sum is σ = 645666372. Its totient is φ = 640147392.

The previous prime is 642906871. The next prime is 642906883. The reversal of 642906881 is 188609246.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 76038400 + 566868481 = 8720^2 + 23809^2 .

It is a cyclic number.

It is not a de Polignac number, because 642906881 - 2¹⁴ = 642890497 is a prime.

It is a super-2 number, since 2×642906881² = 826658515274296322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (642906883) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1379396 + ... + 1379861.

It is an arithmetic number, because the mean of its divisors is an integer number (161416593).

Almost surely, 2^642906881 is an apocalyptic number.

It is an amenable number.

642906881 is a deficient number, since it is larger than the sum of its proper divisors (2759491).

642906881 is a wasteful number, since it uses less digits than its factorization.

642906881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2759490.

The product of its (nonzero) digits is 165888, while the sum is 44.

The square root of 642906881 is about 25355.6084722887. The cubic root of 642906881 is about 863.0766317233.

The spelling of 642906881 in words is "six hundred forty-two million, nine hundred six thousand, eight hundred eighty-one".