688782921 has 4 divisors (see below), whose sum is σ = 918377232. Its totient is φ = 459188612.

The previous prime is 688782917. The next prime is 688782949. The reversal of 688782921 is 129287886.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 688782921 - 2² = 688782917 is a prime.

It is a super-2 number, since 2×688782921² = 948843824522584482, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (688782911) 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, 114797151 + ... + 114797156.

It is an arithmetic number, because the mean of its divisors is an integer number (229594308).

Almost surely, 2^688782921 is an apocalyptic number.

It is an amenable number.

688782921 is a deficient number, since it is larger than the sum of its proper divisors (229594311).

688782921 is a wasteful number, since it uses less digits than its factorization.

688782921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 229594310.

The product of its digits is 774144, while the sum is 51.

The square root of 688782921 is about 26244.6741454338. The cubic root of 688782921 is about 883.1357315523.

The spelling of 688782921 in words is "six hundred eighty-eight million, seven hundred eighty-two thousand, nine hundred twenty-one".