1690921 has 4 divisors (see below), whose sum is σ = 1706832. Its totient is φ = 1675012.

The previous prime is 1690901. The next prime is 1690933. The reversal of 1690921 is 1290961.

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 1690921 - 2¹⁷ = 1559849 is a prime.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

1690921 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 1690921.

It is not an unprimeable number, because it can be changed into a prime (1690901) 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, 7795 + ... + 8008.

It is an arithmetic number, because the mean of its divisors is an integer number (426708).

2^1690921 is an apocalyptic number.

It is an amenable number.

1690921 is a deficient number, since it is larger than the sum of its proper divisors (15911).

1690921 is a wasteful number, since it uses less digits than its factorization.

1690921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15910.

The product of its (nonzero) digits is 972, while the sum is 28.

The square root of 1690921 is about 1300.3541825211. The cubic root of 1690921 is about 119.1354764302.

The spelling of 1690921 in words is "one million, six hundred ninety thousand, nine hundred twenty-one".