21404420309 has 2 divisors, whose sum is σ = 21404420310. Its totient is φ = 21404420308.

The previous prime is 21404420281. The next prime is 21404420321. The reversal of 21404420309 is 90302440412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20560692100 + 843728209 = 143390^2 + 29047^2 .

It is a cyclic number.

It is not a de Polignac number, because 21404420309 - 2¹⁶ = 21404354773 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21404420209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10702210154 + 10702210155.

It is an arithmetic number, because the mean of its divisors is an integer number (10702210155).

Almost surely, 2^21404420309 is an apocalyptic number.

It is an amenable number.

21404420309 is a deficient number, since it is larger than the sum of its proper divisors (1).

21404420309 is an equidigital number, since it uses as much as digits as its factorization.

21404420309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6912, while the sum is 29.

The spelling of 21404420309 in words is "twenty-one billion, four hundred four million, four hundred twenty thousand, three hundred nine".