1687421 has 2 divisors, whose sum is σ = 1687422. Its totient is φ = 1687420.

The previous prime is 1687393. The next prime is 1687451. The reversal of 1687421 is 1247861.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1466521 + 220900 = 1211^2 + 470^2 .

It is an emirp because it is prime and its reverse (1247861) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1687421 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1687451) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 843710 + 843711.

It is an arithmetic number, because the mean of its divisors is an integer number (843711).

2^1687421 is an apocalyptic number.

It is an amenable number.

1687421 is a deficient number, since it is larger than the sum of its proper divisors (1).

1687421 is an equidigital number, since it uses as much as digits as its factorization.

1687421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2688, while the sum is 29.

The square root of 1687421 is about 1299.0076982066. The cubic root of 1687421 is about 119.0532210215.

The spelling of 1687421 in words is "one million, six hundred eighty-seven thousand, four hundred twenty-one".