642739906 has 4 divisors (see below), whose sum is σ = 964109862. Its totient is φ = 321369952.

The previous prime is 642739871. The next prime is 642739921. The reversal of 642739906 is 609937246.

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., 642369025 + 370881 = 25345^2 + 609^2 .

It is a super-2 number, since 2×642739906² = 826229173529777672, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160684975 + ... + 160684978.

Almost surely, 2^642739906 is an apocalyptic number.

642739906 is a deficient number, since it is larger than the sum of its proper divisors (321369956).

642739906 is a wasteful number, since it uses less digits than its factorization.

642739906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 321369955.

The product of its (nonzero) digits is 489888, while the sum is 46.

The square root of 642739906 is about 25352.3155944383. The cubic root of 642739906 is about 863.0019061797.

The spelling of 642739906 in words is "six hundred forty-two million, seven hundred thirty-nine thousand, nine hundred six".