21216738 has 8 divisors (see below), whose sum is σ = 42433488. Its totient is φ = 7072244.

The previous prime is 21216737. The next prime is 21216739. The reversal of 21216738 is 83761212.

It is an interprime number because it is at equal distance from previous prime (21216737) and next prime (21216739).

It is a sphenic number, since it is the product of 3 distinct primes.

21216738 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21216737) 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, 1768056 + ... + 1768067.

It is an arithmetic number, because the mean of its divisors is an integer number (5304186).

Almost surely, 2^21216738 is an apocalyptic number.

21216738 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21216738 is a wasteful number, since it uses less digits than its factorization.

21216738 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3536128.

The product of its digits is 4032, while the sum is 30.

The square root of 21216738 is about 4606.1630453122. The cubic root of 21216738 is about 276.8383196333.

The spelling of 21216738 in words is "twenty-one million, two hundred sixteen thousand, seven hundred thirty-eight".