161221621 has 4 divisors (see below), whose sum is σ = 175878144. Its totient is φ = 146565100.

The previous prime is 161221603. The next prime is 161221667. The reversal of 161221621 is 126122161.

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 not a de Polignac number, because 161221621 - 2¹¹ = 161219573 is a prime.

It is a super-2 number, since 2×161221621² = 51984822155735282, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 161221592 and 161221601.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161221681) 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, 7328245 + ... + 7328266.

It is an arithmetic number, because the mean of its divisors is an integer number (43969536).

Almost surely, 2^161221621 is an apocalyptic number.

161221621 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

161221621 is a deficient number, since it is larger than the sum of its proper divisors (14656523).

161221621 is a wasteful number, since it uses less digits than its factorization.

161221621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14656522.

The product of its digits is 288, while the sum is 22.

The square root of 161221621 is about 12697.3076279974. The cubic root of 161221621 is about 544.2616840861.

Adding to 161221621 its reverse (126122161), we get a palindrome (287343782).

The spelling of 161221621 in words is "one hundred sixty-one million, two hundred twenty-one thousand, six hundred twenty-one".