20161621 has 4 divisors (see below), whose sum is σ = 20346700. Its totient is φ = 19976544.

The previous prime is 20161619. The next prime is 20161649. The reversal of 20161621 is 12616102.

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 14212900 + 5948721 = 3770^2 + 2439^2 .

It is a cyclic number.

It is not a de Polignac number, because 20161621 - 2¹ = 20161619 is a prime.

It is a super-2 number, since 2×20161621² = 812981922695282, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20161601) 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, 92376 + ... + 92593.

It is an arithmetic number, because the mean of its divisors is an integer number (5086675).

Almost surely, 2^20161621 is an apocalyptic number.

It is an amenable number.

20161621 is a deficient number, since it is larger than the sum of its proper divisors (185079).

20161621 is a wasteful number, since it uses less digits than its factorization.

20161621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 185078.

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 20161621 is about 4490.1693731974. The cubic root of 20161621 is about 272.1709790414.

Adding to 20161621 its reverse (12616102), we get a palindrome (32777723).

The spelling of 20161621 in words is "twenty million, one hundred sixty-one thousand, six hundred twenty-one".