1640921 has 4 divisors (see below), whose sum is σ = 1651152. Its totient is φ = 1630692.

The previous prime is 1640887. The next prime is 1640927. The reversal of 1640921 is 1290461.

It is a happy number.

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 1640921 - 2¹⁸ = 1378777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1640927) 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, 4871 + ... + 5196.

It is an arithmetic number, because the mean of its divisors is an integer number (412788).

2^1640921 is an apocalyptic number.

It is an amenable number.

1640921 is a deficient number, since it is larger than the sum of its proper divisors (10231).

1640921 is a wasteful number, since it uses less digits than its factorization.

1640921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10230.

The product of its (nonzero) digits is 432, while the sum is 23.

The square root of 1640921 is about 1280.9843871024. The cubic root of 1640921 is about 117.9494420968.

The spelling of 1640921 in words is "one million, six hundred forty thousand, nine hundred twenty-one".