161641621 has 4 divisors (see below), whose sum is σ = 167215500. Its totient is φ = 156067744.

The previous prime is 161641591. The next prime is 161641633. The reversal of 161641621 is 126146161.

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 32364721 + 129276900 = 5689^2 + 11370^2 .

It is a cyclic number.

It is not a de Polignac number, because 161641621 - 2¹³ = 161633429 is a prime.

It is a super-2 number, since 2×161641621² = 52256027279015282, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 161641621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161641681) 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, 2786896 + ... + 2786953.

It is an arithmetic number, because the mean of its divisors is an integer number (41803875).

Almost surely, 2^161641621 is an apocalyptic number.

It is an amenable number.

161641621 is a deficient number, since it is larger than the sum of its proper divisors (5573879).

161641621 is an equidigital number, since it uses as much as digits as its factorization.

161641621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5573878.

The product of its digits is 1728, while the sum is 28.

The square root of 161641621 is about 12713.8358098569. The cubic root of 161641621 is about 544.7338947240.

Adding to 161641621 its reverse (126146161), we get a palindrome (287787782).

The spelling of 161641621 in words is "one hundred sixty-one million, six hundred forty-one thousand, six hundred twenty-one".