21122009 has 2 divisors, whose sum is σ = 21122010. Its totient is φ = 21122008.

The previous prime is 21121999. The next prime is 21122033. The reversal of 21122009 is 90022112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15960025 + 5161984 = 3995^2 + 2272^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21122009 is a prime.

It is a super-2 number, since 2×21122009² = 892278528392162, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21122069) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561004 + 10561005.

It is an arithmetic number, because the mean of its divisors is an integer number (10561005).

Almost surely, 2^21122009 is an apocalyptic number.

It is an amenable number.

21122009 is a deficient number, since it is larger than the sum of its proper divisors (1).

21122009 is an equidigital number, since it uses as much as digits as its factorization.

21122009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 72, while the sum is 17.

The square root of 21122009 is about 4595.8686882895. The cubic root of 21122009 is about 276.4256934682.

The spelling of 21122009 in words is "twenty-one million, one hundred twenty-two thousand, nine".