21091009001 has 2 divisors, whose sum is σ = 21091009002. Its totient is φ = 21091009000.

The previous prime is 21091008977. The next prime is 21091009007. The reversal of 21091009001 is 10090019012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17357799001 + 3733210000 = 131749^2 + 61100^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21091009001 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21091009007) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10545504500 + 10545504501.

It is an arithmetic number, because the mean of its divisors is an integer number (10545504501).

Almost surely, 2^21091009001 is an apocalyptic number.

It is an amenable number.

21091009001 is a deficient number, since it is larger than the sum of its proper divisors (1).

21091009001 is an equidigital number, since it uses as much as digits as its factorization.

21091009001 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 162, while the sum is 23.

The spelling of 21091009001 in words is "twenty-one billion, ninety-one million, nine thousand, one".