21002434009 has 4 divisors (see below), whose sum is σ = 21007326004. Its totient is φ = 20997542016.

The previous prime is 21002434003. The next prime is 21002434021. The reversal of 21002434009 is 90043420012.

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 8322547984 + 12679886025 = 91228^2 + 112605^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21002434009 is a prime.

It is a super-2 number, since 2×21002434009² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21002434003) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2439552 + ... + 2448145.

It is an arithmetic number, because the mean of its divisors is an integer number (5251831501).

Almost surely, 2^21002434009 is an apocalyptic number.

It is an amenable number.

21002434009 is a deficient number, since it is larger than the sum of its proper divisors (4891995).

21002434009 is an equidigital number, since it uses as much as digits as its factorization.

21002434009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4891994.

The product of its (nonzero) digits is 1728, while the sum is 25.

The spelling of 21002434009 in words is "twenty-one billion, two million, four hundred thirty-four thousand, nine".