21197709 has 24 divisors (see below), whose sum is σ = 33313280. Its totient is φ = 12910752.

The previous prime is 21197699. The next prime is 21197731. The reversal of 21197709 is 90779112.

It is not a de Polignac number, because 21197709 - 2⁵ = 21197677 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21192709) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11172 + ... + 12930.

Almost surely, 2^21197709 is an apocalyptic number.

It is an amenable number.

21197709 is a deficient number, since it is larger than the sum of its proper divisors (12115571).

21197709 is a wasteful number, since it uses less digits than its factorization.

21197709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1881 (or 1878 counting only the distinct ones).

The product of its (nonzero) digits is 7938, while the sum is 36.

The square root of 21197709 is about 4604.0969798648. The cubic root of 21197709 is about 276.7555307194.

The spelling of 21197709 in words is "twenty-one million, one hundred ninety-seven thousand, seven hundred nine".