688687994 has 4 divisors (see below), whose sum is σ = 1033031994. Its totient is φ = 344343996.

The previous prime is 688687981. The next prime is 688687999. The reversal of 688687994 is 499786886.

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., 672727969 + 15960025 = 25937^2 + 3995^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 688687994.

It is not an unprimeable number, because it can be changed into a prime (688687999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 172171997 + ... + 172172000.

Almost surely, 2^688687994 is an apocalyptic number.

688687994 is a deficient number, since it is larger than the sum of its proper divisors (344344000).

688687994 is a wasteful number, since it uses less digits than its factorization.

688687994 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 344343999.

The product of its digits is 41803776, while the sum is 65.

The square root of 688687994 is about 26242.8655828589. The cubic root of 688687994 is about 883.0951588868.

The spelling of 688687994 in words is "six hundred eighty-eight million, six hundred eighty-seven thousand, nine hundred ninety-four".