21492409 has 2 divisors, whose sum is σ = 21492410. Its totient is φ = 21492408.

The previous prime is 21492379. The next prime is 21492413. The reversal of 21492409 is 90429412.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21132409 + 360000 = 4597^2 + 600^2 .

It is a cyclic number.

It is not a de Polignac number, because 21492409 - 2²³ = 13103801 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21492469) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10746204 + 10746205.

It is an arithmetic number, because the mean of its divisors is an integer number (10746205).

Almost surely, 2^21492409 is an apocalyptic number.

It is an amenable number.

21492409 is a deficient number, since it is larger than the sum of its proper divisors (1).

21492409 is an equidigital number, since it uses as much as digits as its factorization.

21492409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 21492409 is about 4635.9906169016. The cubic root of 21492409 is about 278.0321590387.

The spelling of 21492409 in words is "twenty-one million, four hundred ninety-two thousand, four hundred nine".