1921639 has 4 divisors (see below), whose sum is σ = 1936440. Its totient is φ = 1906840.

The previous prime is 1921631. The next prime is 1921657. The reversal of 1921639 is 9361291.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9361291 = 229 ⋅40879.

It is a cyclic number.

It is not a de Polignac number, because 1921639 - 2³ = 1921631 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1921639.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1921631) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7204 + ... + 7465.

It is an arithmetic number, because the mean of its divisors is an integer number (484110).

2^1921639 is an apocalyptic number.

1921639 is a deficient number, since it is larger than the sum of its proper divisors (14801).

1921639 is a wasteful number, since it uses less digits than its factorization.

1921639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14800.

The product of its digits is 2916, while the sum is 31.

The square root of 1921639 is about 1386.2319430745. The cubic root of 1921639 is about 124.3246565272.

The spelling of 1921639 in words is "one million, nine hundred twenty-one thousand, six hundred thirty-nine".