21688337 has 4 divisors (see below), whose sum is σ = 23660016. Its totient is φ = 19716660.

The previous prime is 21688307. The next prime is 21688343. The reversal of 21688337 is 73388612.

It is a happy number.

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.

It is a cyclic number.

It is not a de Polignac number, because 21688337 - 2¹² = 21684241 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21688337.

It is not an unprimeable number, because it can be changed into a prime (21688307) 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, 985823 + ... + 985844.

It is an arithmetic number, because the mean of its divisors is an integer number (5915004).

Almost surely, 2^21688337 is an apocalyptic number.

It is an amenable number.

21688337 is a deficient number, since it is larger than the sum of its proper divisors (1971679).

21688337 is a wasteful number, since it uses less digits than its factorization.

21688337 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1971678.

The product of its digits is 48384, while the sum is 38.

The square root of 21688337 is about 4657.0738667107. The cubic root of 21688337 is about 278.8744655206.

The spelling of 21688337 in words is "twenty-one million, six hundred eighty-eight thousand, three hundred thirty-seven".