161621 has 4 divisors (see below), whose sum is σ = 168672. Its totient is φ = 154572.

The previous prime is 161611. The next prime is 161627. The reversal of 161621 is 126161.

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 a de Polignac number, because none of the positive numbers 2^k-161621 is a prime.

It is a super-2 number, since 2×161621² = 52242695282, which contains 22 as substring.

It is a Duffinian number.

161621 is a modest number, since divided by 621 gives 161 as remainder.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 161621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161627) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3491 + ... + 3536.

It is an arithmetic number, because the mean of its divisors is an integer number (42168).

2¹⁶¹⁶²¹ is an apocalyptic number.

It is an amenable number.

161621 is a deficient number, since it is larger than the sum of its proper divisors (7051).

161621 is an equidigital number, since it uses as much as digits as its factorization.

161621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7050.

The product of its digits is 72, while the sum is 17.

The square root of 161621 is about 402.0211437226. The cubic root of 161621 is about 54.4710729413.

Subtracting from 161621 its sum of digits (17), we obtain a square (161604 = 402²).

Adding to 161621 its reverse (126161), we get a palindrome (287782).

The spelling of 161621 in words is "one hundred sixty-one thousand, six hundred twenty-one".