20260721 has 4 divisors (see below), whose sum is σ = 21819252. Its totient is φ = 18702192.

The previous prime is 20260703. The next prime is 20260729. The reversal of 20260721 is 12706202.

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 2283121 + 17977600 = 1511^2 + 4240^2 .

It is a cyclic number.

It is not a de Polignac number, because 20260721 - 2¹⁴ = 20244337 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 20260693 and 20260702.

It is not an unprimeable number, because it can be changed into a prime (20260729) 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, 779246 + ... + 779271.

It is an arithmetic number, because the mean of its divisors is an integer number (5454813).

Almost surely, 2^20260721 is an apocalyptic number.

It is an amenable number.

20260721 is a deficient number, since it is larger than the sum of its proper divisors (1558531).

20260721 is a wasteful number, since it uses less digits than its factorization.

20260721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1558530.

The product of its (nonzero) digits is 336, while the sum is 20.

The square root of 20260721 is about 4501.1910645961. The cubic root of 20260721 is about 272.6161825368.

Adding to 20260721 its reverse (12706202), we get a palindrome (32966923).

The spelling of 20260721 in words is "twenty million, two hundred sixty thousand, seven hundred twenty-one".