1620221 has 4 divisors (see below), whose sum is σ = 1646844. Its totient is φ = 1593600.

The previous prime is 1620217. The next prime is 1620233. The reversal of 1620221 is 1220261.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 648025 + 972196 = 805^2 + 986^2 .

It is a cyclic number.

It is not a de Polignac number, because 1620221 - 2² = 1620217 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1620196 and 1620205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1620251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13220 + ... + 13341.

It is an arithmetic number, because the mean of its divisors is an integer number (411711).

2^1620221 is an apocalyptic number.

It is an amenable number.

1620221 is a deficient number, since it is larger than the sum of its proper divisors (26623).

1620221 is an equidigital number, since it uses as much as digits as its factorization.

1620221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26622.

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 1620221 is about 1272.8790201743. The cubic root of 1620221 is about 117.4513696450.

Adding to 1620221 its reverse (1220261), we get a palindrome (2840482).

The spelling of 1620221 in words is "one million, six hundred twenty thousand, two hundred twenty-one".