21271409 has 2 divisors, whose sum is σ = 21271410. Its totient is φ = 21271408.

The previous prime is 21271381. The next prime is 21271423. The reversal of 21271409 is 90417212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18515809 + 2755600 = 4303^2 + 1660^2 .

It is a cyclic number.

It is not a de Polignac number, because 21271409 - 2⁸ = 21271153 is a prime.

It is not a weakly prime, because it can be changed into another prime (21271429) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10635704 + 10635705.

It is an arithmetic number, because the mean of its divisors is an integer number (10635705).

Almost surely, 2^21271409 is an apocalyptic number.

It is an amenable number.

21271409 is a deficient number, since it is larger than the sum of its proper divisors (1).

21271409 is an equidigital number, since it uses as much as digits as its factorization.

21271409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1008, while the sum is 26.

The square root of 21271409 is about 4612.0937761498. The cubic root of 21271409 is about 277.0759000826.

The spelling of 21271409 in words is "twenty-one million, two hundred seventy-one thousand, four hundred nine".