20216621 has 4 divisors (see below), whose sum is σ = 21405852. Its totient is φ = 19027392.

The previous prime is 20216593. The next prime is 20216633. The reversal of 20216621 is 12661202.

It is a happy number.

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 7155625 + 13060996 = 2675^2 + 3614^2 .

It is a cyclic number.

It is not a de Polignac number, because 20216621 - 2¹⁴ = 20200237 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20216593 and 20216602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20216641) 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, 594590 + ... + 594623.

It is an arithmetic number, because the mean of its divisors is an integer number (5351463).

Almost surely, 2^20216621 is an apocalyptic number.

It is an amenable number.

20216621 is a deficient number, since it is larger than the sum of its proper divisors (1189231).

20216621 is a wasteful number, since it uses less digits than its factorization.

20216621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1189230.

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 20216621 is about 4496.2896926244. The cubic root of 20216621 is about 272.4182444189.

Adding to 20216621 its reverse (12661202), we get a palindrome (32877823).

The spelling of 20216621 in words is "twenty million, two hundred sixteen thousand, six hundred twenty-one".