687437921 has 4 divisors (see below), whose sum is σ = 687985200. Its totient is φ = 686890644.

The previous prime is 687437903. The next prime is 687437923. The reversal of 687437921 is 129734786.

687437921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 a de Polignac number, because none of the positive numbers 2^k-687437921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (687437923) 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, 271751 + ... + 274268.

It is an arithmetic number, because the mean of its divisors is an integer number (171996300).

Almost surely, 2^687437921 is an apocalyptic number.

It is an amenable number.

687437921 is a deficient number, since it is larger than the sum of its proper divisors (547279).

687437921 is a wasteful number, since it uses less digits than its factorization.

687437921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 547278.

The product of its digits is 508032, while the sum is 47.

The square root of 687437921 is about 26219.0373774477. The cubic root of 687437921 is about 882.5605181235.

The spelling of 687437921 in words is "six hundred eighty-seven million, four hundred thirty-seven thousand, nine hundred twenty-one".