21197839 has 12 divisors (see below), whose sum is σ = 23495736. Its totient is φ = 19105632.

The previous prime is 21197837. The next prime is 21197851. The reversal of 21197839 is 93879112.

It is not a de Polignac number, because 21197839 - 2¹ = 21197837 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 (21197837) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5809 + ... + 8725.

It is an arithmetic number, because the mean of its divisors is an integer number (1957978).

Almost surely, 2^21197839 is an apocalyptic number.

21197839 is a deficient number, since it is larger than the sum of its proper divisors (2297897).

21197839 is a wasteful number, since it uses less digits than its factorization.

21197839 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2986 (or 2973 counting only the distinct ones).

The product of its digits is 27216, while the sum is 40.

The square root of 21197839 is about 4604.1110977039. Note that the first 3 decimals coincide. The cubic root of 21197839 is about 276.7560964746.

The spelling of 21197839 in words is "twenty-one million, one hundred ninety-seven thousand, eight hundred thirty-nine".