1687944421 has 8 divisors (see below), whose sum is σ = 1706974488. Its totient is φ = 1668960000.

The previous prime is 1687944409. The next prime is 1687944437. The reversal of 1687944421 is 1244497861.

It can be written as a sum of positive squares in 4 ways, for example, as 350213796 + 1337730625 = 18714^2 + 36575^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a 4-Lehmer number, since φ(1687944421) divides (1687944421-1)⁴.

It is a cyclic number.

It is not a de Polignac number, because 1687944421 - 2⁹ = 1687943909 is a prime.

It is a deceptive number, since it divides R_1687944420.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1687944491) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 65881 + ... + 87841.

It is an arithmetic number, because the mean of its divisors is an integer number (213371811).

Almost surely, 2^1687944421 is an apocalyptic number.

1687944421 is the 21961-st nonagonal number.

It is an amenable number.

1687944421 is a deficient number, since it is larger than the sum of its proper divisors (19030067).

1687944421 is a wasteful number, since it uses less digits than its factorization.

1687944421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22823.

The product of its digits is 387072, while the sum is 46.

The square root of 1687944421 is about 41084.6007769334. The cubic root of 1687944421 is about 1190.6552945229.

The spelling of 1687944421 in words is "one billion, six hundred eighty-seven million, nine hundred forty-four thousand, four hundred twenty-one".