21023402009 has 2 divisors, whose sum is σ = 21023402010. Its totient is φ = 21023402008.

The previous prime is 21023401999. The next prime is 21023402033. The reversal of 21023402009 is 90020432012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13195576384 + 7827825625 = 114872^2 + 88475^2 .

It is a cyclic number.

It is not a de Polignac number, because 21023402009 - 2⁸ = 21023401753 is a prime.

It is not a weakly prime, because it can be changed into another prime (21023404009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10511701004 + 10511701005.

It is an arithmetic number, because the mean of its divisors is an integer number (10511701005).

Almost surely, 2^21023402009 is an apocalyptic number.

It is an amenable number.

21023402009 is a deficient number, since it is larger than the sum of its proper divisors (1).

21023402009 is an equidigital number, since it uses as much as digits as its factorization.

21023402009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 864, while the sum is 23.

The spelling of 21023402009 in words is "twenty-one billion, twenty-three million, four hundred two thousand, nine".