20440165621 has 2 divisors, whose sum is σ = 20440165622. Its totient is φ = 20440165620.

The previous prime is 20440165597. The next prime is 20440165631. The reversal of 20440165621 is 12656104402.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15858364900 + 4581800721 = 125930^2 + 67689^2 .

It is a cyclic number.

It is not a de Polignac number, because 20440165621 - 2¹³ = 20440157429 is a prime.

It is a super-2 number, since 2×20440165621² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20440165631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10220082810 + 10220082811.

It is an arithmetic number, because the mean of its divisors is an integer number (10220082811).

Almost surely, 2^20440165621 is an apocalyptic number.

It is an amenable number.

20440165621 is a deficient number, since it is larger than the sum of its proper divisors (1).

20440165621 is an equidigital number, since it uses as much as digits as its factorization.

20440165621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11520, while the sum is 31.

The spelling of 20440165621 in words is "twenty billion, four hundred forty million, one hundred sixty-five thousand, six hundred twenty-one".