21404729 has 2 divisors, whose sum is σ = 21404730. Its totient is φ = 21404728.

The previous prime is 21404689. The next prime is 21404731. The reversal of 21404729 is 92740412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20839225 + 565504 = 4565^2 + 752^2 .

It is a cyclic number.

It is not a de Polignac number, because 21404729 - 2²⁰ = 20356153 is a prime.

Together with 21404731, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21404029) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10702364 + 10702365.

It is an arithmetic number, because the mean of its divisors is an integer number (10702365).

Almost surely, 2^21404729 is an apocalyptic number.

It is an amenable number.

21404729 is a deficient number, since it is larger than the sum of its proper divisors (1).

21404729 is an equidigital number, since it uses as much as digits as its factorization.

21404729 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4032, while the sum is 29.

The square root of 21404729 is about 4626.5245055009. The cubic root of 21404729 is about 277.6535589243.

The spelling of 21404729 in words is "twenty-one million, four hundred four thousand, seven hundred twenty-nine".