642821386 has 4 divisors (see below), whose sum is σ = 964232082. Its totient is φ = 321410692.

The previous prime is 642821381. The next prime is 642821423. The reversal of 642821386 is 683128246.

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

It can be written as a sum of positive squares in only one way, i.e., 618467161 + 24354225 = 24869^2 + 4935^2 .

It is not an unprimeable number, because it can be changed into a prime (642821381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160705345 + ... + 160705348.

Almost surely, 2^642821386 is an apocalyptic number.

642821386 is a deficient number, since it is larger than the sum of its proper divisors (321410696).

642821386 is a wasteful number, since it uses less digits than its factorization.

642821386 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 321410695.

The product of its digits is 110592, while the sum is 40.

The square root of 642821386 is about 25353.9224973178. The cubic root of 642821386 is about 863.0383721610.

The spelling of 642821386 in words is "six hundred forty-two million, eight hundred twenty-one thousand, three hundred eighty-six".