1990921 has 9 divisors (see below), whose sum is σ = 2140711. Its totient is φ = 1851232.

The previous prime is 1990907. The next prime is 1990927. The reversal of 1990921 is 1290991.

The square root of 1990921 is 1411.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 1550025 + 440896 = 1245^2 + 664^2 .

It is not a de Polignac number, because 1990921 - 2⁵ = 1990889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1990927) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 23946 + ... + 24028.

2^1990921 is an apocalyptic number.

1990921 is the 1411-st square number.

1990921 is the 706-th centered octagonal number.

It is an amenable number.

1990921 is a deficient number, since it is larger than the sum of its proper divisors (149790).

1990921 is an frugal number, since it uses more digits than its factorization.

1990921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 200 (or 100 counting only the distinct ones).

The product of its (nonzero) digits is 1458, while the sum is 31.

The cubic root of 1990921 is about 125.8011687254.

The spelling of 1990921 in words is "one million, nine hundred ninety thousand, nine hundred twenty-one".