21349709 has 4 divisors (see below), whose sum is σ = 21359520. Its totient is φ = 21339900.

The previous prime is 21349697. The next prime is 21349717. The reversal of 21349709 is 90794312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21349709 - 2⁸ = 21349453 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21349729) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17 + ... + 6534.

It is an arithmetic number, because the mean of its divisors is an integer number (5339880).

Almost surely, 2^21349709 is an apocalyptic number.

It is an amenable number.

21349709 is a deficient number, since it is larger than the sum of its proper divisors (9811).

21349709 is an equidigital number, since it uses as much as digits as its factorization.

21349709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9810.

The product of its (nonzero) digits is 13608, while the sum is 35.

The square root of 21349709 is about 4620.5745313759. The cubic root of 21349709 is about 277.4154556724.

The spelling of 21349709 in words is "twenty-one million, three hundred forty-nine thousand, seven hundred nine".