21251002109 has 2 divisors, whose sum is σ = 21251002110. Its totient is φ = 21251002108.

The previous prime is 21251002103. The next prime is 21251002117. The reversal of 21251002109 is 90120015212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18699742009 + 2551260100 = 136747^2 + 50510^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21251002109 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21251002103) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10625501054 + 10625501055.

It is an arithmetic number, because the mean of its divisors is an integer number (10625501055).

Almost surely, 2^21251002109 is an apocalyptic number.

It is an amenable number.

21251002109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21251002109 is an equidigital number, since it uses as much as digits as its factorization.

21251002109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 360, while the sum is 23.

The spelling of 21251002109 in words is "twenty-one billion, two hundred fifty-one million, two thousand, one hundred nine".