21197684 has 6 divisors (see below), whose sum is σ = 37095954. Its totient is φ = 10598840.

The previous prime is 21197681. The next prime is 21197699. The reversal of 21197684 is 48679112.

It can be written as a sum of positive squares in only one way, i.e., 16224784 + 4972900 = 4028^2 + 2230^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21197681) 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 as a sum of consecutive naturals, namely, 2649707 + ... + 2649714.

It is an arithmetic number, because the mean of its divisors is an integer number (6182659).

Almost surely, 2^21197684 is an apocalyptic number.

It is an amenable number.

21197684 is a deficient number, since it is larger than the sum of its proper divisors (15898270).

21197684 is a wasteful number, since it uses less digits than its factorization.

21197684 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5299425 (or 5299423 counting only the distinct ones).

The product of its digits is 24192, while the sum is 38.

The square root of 21197684 is about 4604.0942648908. The cubic root of 21197684 is about 276.7554219200.

The spelling of 21197684 in words is "twenty-one million, one hundred ninety-seven thousand, six hundred eighty-four".