20801621 has 4 divisors (see below), whose sum is σ = 20960544. Its totient is φ = 20642700.

The previous prime is 20801617. The next prime is 20801629. The reversal of 20801621 is 12610802.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12610802 = 2 ⋅6305401.

It is a cyclic number.

It is not a de Polignac number, because 20801621 - 2² = 20801617 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20801593 and 20801602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20801629) 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, 79265 + ... + 79526.

It is an arithmetic number, because the mean of its divisors is an integer number (5240136).

Almost surely, 2^20801621 is an apocalyptic number.

It is an amenable number.

20801621 is a deficient number, since it is larger than the sum of its proper divisors (158923).

20801621 is a wasteful number, since it uses less digits than its factorization.

20801621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158922.

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 20801621 is about 4560.8794108154. The cubic root of 20801621 is about 275.0209174172.

The spelling of 20801621 in words is "twenty million, eight hundred one thousand, six hundred twenty-one".