1681639 has 2 divisors, whose sum is σ = 1681640. Its totient is φ = 1681638.

The previous prime is 1681621. The next prime is 1681649. The reversal of 1681639 is 9361861.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1681639 - 2¹³ = 1673447 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1681619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 840819 + 840820.

It is an arithmetic number, because the mean of its divisors is an integer number (840820).

2^1681639 is an apocalyptic number.

1681639 is a deficient number, since it is larger than the sum of its proper divisors (1).

1681639 is an equidigital number, since it uses as much as digits as its factorization.

1681639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7776, while the sum is 34.

The square root of 1681639 is about 1296.7802435262. The cubic root of 1681639 is about 118.9170855699.

The spelling of 1681639 in words is "one million, six hundred eighty-one thousand, six hundred thirty-nine".