21102009989 has 2 divisors, whose sum is σ = 21102009990. Its totient is φ = 21102009988.

The previous prime is 21102009983. The next prime is 21102010009. The reversal of 21102009989 is 98990020112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16697033089 + 4404976900 = 129217^2 + 66370^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21102009989 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21102009983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10551004994 + 10551004995.

It is an arithmetic number, because the mean of its divisors is an integer number (10551004995).

Almost surely, 2^21102009989 is an apocalyptic number.

It is an amenable number.

21102009989 is a deficient number, since it is larger than the sum of its proper divisors (1).

21102009989 is an equidigital number, since it uses as much as digits as its factorization.

21102009989 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23328, while the sum is 41.

The spelling of 21102009989 in words is "twenty-one billion, one hundred two million, nine thousand, nine hundred eighty-nine".