20442721 has 16 divisors (see below), whose sum is σ = 23469264. Its totient is φ = 17639424.

The previous prime is 20442713. The next prime is 20442731. The reversal of 20442721 is 12724402.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 291600 + 20151121 = 540^2 + 4489^2 .

It is a cyclic number.

It is not a de Polignac number, because 20442721 - 2³ = 20442713 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20442692 and 20442701.

It is not an unprimeable number, because it can be changed into a prime (20442731) 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, 51295 + ... + 51691.

It is an arithmetic number, because the mean of its divisors is an integer number (1466829).

Almost surely, 2^20442721 is an apocalyptic number.

It is an amenable number.

20442721 is a deficient number, since it is larger than the sum of its proper divisors (3026543).

20442721 is a wasteful number, since it uses less digits than its factorization.

20442721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 660.

The product of its (nonzero) digits is 896, while the sum is 22.

The square root of 20442721 is about 4521.3627370517. The cubic root of 20442721 is about 273.4300449298.

The spelling of 20442721 in words is "twenty million, four hundred forty-two thousand, seven hundred twenty-one".