20761221 has 16 divisors (see below), whose sum is σ = 29894144. Its totient is φ = 12740544.

The previous prime is 20761207. The next prime is 20761229. The reversal of 20761221 is 12216702.

It is not a de Polignac number, because 20761221 - 2⁷ = 20761093 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20761229) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 23235 + ... + 24111.

It is an arithmetic number, because the mean of its divisors is an integer number (1868384).

Almost surely, 2^20761221 is an apocalyptic number.

20761221 is the 2631-st octagonal number.

It is an amenable number.

20761221 is a deficient number, since it is larger than the sum of its proper divisors (9132923).

20761221 is a wasteful number, since it uses less digits than its factorization.

20761221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1500.

The product of its (nonzero) digits is 336, while the sum is 21.

The square root of 20761221 is about 4556.4482878663. The cubic root of 20761221 is about 274.8427574902.

Adding to 20761221 its reverse (12216702), we get a palindrome (32977923).

The spelling of 20761221 in words is "twenty million, seven hundred sixty-one thousand, two hundred twenty-one".