1687323721 has 4 divisors (see below), whose sum is σ = 1687484944. Its totient is φ = 1687162500.

The previous prime is 1687323719. The next prime is 1687323739. The reversal of 1687323721 is 1273237861.

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 1687323721 - 2¹ = 1687323719 is a prime.

It is a super-2 number, since 2×1687323721² = 5694122678898571682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1687323221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 63735 + ... + 86236.

It is an arithmetic number, because the mean of its divisors is an integer number (421871236).

Almost surely, 2^1687323721 is an apocalyptic number.

It is an amenable number.

1687323721 is a deficient number, since it is larger than the sum of its proper divisors (161223).

1687323721 is a wasteful number, since it uses less digits than its factorization.

1687323721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 161222.

The product of its digits is 84672, while the sum is 40.

The square root of 1687323721 is about 41077.0461571910. The cubic root of 1687323721 is about 1190.5093319074.

The spelling of 1687323721 in words is "one billion, six hundred eighty-seven million, three hundred twenty-three thousand, seven hundred twenty-one".