20402440021 has 4 divisors (see below), whose sum is σ = 20443993344. Its totient is φ = 20360886700.

The previous prime is 20402439997. The next prime is 20402440067. The reversal of 20402440021 is 12004420402.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20402440021 - 2¹¹ = 20402437973 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 (20402440321) 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, 20775925 + ... + 20776906.

It is an arithmetic number, because the mean of its divisors is an integer number (5110998336).

Almost surely, 2^20402440021 is an apocalyptic number.

It is an amenable number.

20402440021 is a deficient number, since it is larger than the sum of its proper divisors (41553323).

20402440021 is an equidigital number, since it uses as much as digits as its factorization.

20402440021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41553322.

The product of its (nonzero) digits is 512, while the sum is 19.

Adding to 20402440021 its reverse (12004420402), we get a palindrome (32406860423).

The spelling of 20402440021 in words is "twenty billion, four hundred two million, four hundred forty thousand, twenty-one".