20154721 has 4 divisors (see below), whose sum is σ = 20181700. Its totient is φ = 20127744.

The previous prime is 20154709. The next prime is 20154727. The reversal of 20154721 is 12745102.

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 7623121 + 12531600 = 2761^2 + 3540^2 .

It is a cyclic number.

It is not a de Polignac number, because 20154721 - 2⁵ = 20154689 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20154692 and 20154701.

It is not an unprimeable number, because it can be changed into a prime (20154727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12336 + ... + 13873.

It is an arithmetic number, because the mean of its divisors is an integer number (5045425).

Almost surely, 2^20154721 is an apocalyptic number.

It is an amenable number.

20154721 is a deficient number, since it is larger than the sum of its proper divisors (26979).

20154721 is an equidigital number, since it uses as much as digits as its factorization.

20154721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26978.

The product of its (nonzero) digits is 560, while the sum is 22.

The square root of 20154721 is about 4489.4009622666. The cubic root of 20154721 is about 272.1399267427.

Adding to 20154721 its reverse (12745102), we get a palindrome (32899823).

The spelling of 20154721 in words is "twenty million, one hundred fifty-four thousand, seven hundred twenty-one".