20919221 has 4 divisors (see below), whose sum is σ = 21126444. Its totient is φ = 20712000.

The previous prime is 20919211. The next prime is 20919229. The reversal of 20919221 is 12291902.

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 18232900 + 2686321 = 4270^2 + 1639^2 .

It is a cyclic number.

It is not a de Polignac number, because 20919221 - 2¹⁰ = 20918197 is a prime.

It is a super-2 number, since 2×20919221² = 875227614493682, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20919229) 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, 103460 + ... + 103661.

It is an arithmetic number, because the mean of its divisors is an integer number (5281611).

Almost surely, 2^20919221 is an apocalyptic number.

It is an amenable number.

20919221 is a deficient number, since it is larger than the sum of its proper divisors (207223).

20919221 is a wasteful number, since it uses less digits than its factorization.

20919221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 207222.

The product of its (nonzero) digits is 648, while the sum is 26.

The square root of 20919221 is about 4573.7534913898. The cubic root of 20919221 is about 275.5382120749.

The spelling of 20919221 in words is "twenty million, nine hundred nineteen thousand, two hundred twenty-one".