1663621 has 4 divisors (see below), whose sum is σ = 1751200. Its totient is φ = 1576044.

The previous prime is 1663619. The next prime is 1663681. The reversal of 1663621 is 1263661.

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 1663621 - 2¹ = 1663619 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1663681) 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, 43761 + ... + 43798.

It is an arithmetic number, because the mean of its divisors is an integer number (437800).

2^1663621 is an apocalyptic number.

It is an amenable number.

1663621 is a deficient number, since it is larger than the sum of its proper divisors (87579).

1663621 is an equidigital number, since it uses as much as digits as its factorization.

1663621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87578.

The product of its digits is 1296, while the sum is 25.

The square root of 1663621 is about 1289.8143277232. The cubic root of 1663621 is about 118.4908453704.

The spelling of 1663621 in words is "one million, six hundred sixty-three thousand, six hundred twenty-one".