21709429 has 16 divisors (see below), whose sum is σ = 25833600. Its totient is φ = 17849664.

The previous prime is 21709411. The next prime is 21709433. The reversal of 21709429 is 92490712.

It is a happy number.

It is not a de Polignac number, because 21709429 - 2⁷ = 21709301 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21709394 and 21709403.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21709409) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 46254 + ... + 46720.

It is an arithmetic number, because the mean of its divisors is an integer number (1614600).

Almost surely, 2^21709429 is an apocalyptic number.

21709429 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21709429 is a deficient number, since it is larger than the sum of its proper divisors (4124171).

21709429 is a wasteful number, since it uses less digits than its factorization.

21709429 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 732.

The product of its (nonzero) digits is 9072, while the sum is 34.

The square root of 21709429 is about 4659.3378284902. The cubic root of 21709429 is about 278.9648384323.

The spelling of 21709429 in words is "twenty-one million, seven hundred nine thousand, four hundred twenty-nine".