21523738 has 4 divisors (see below), whose sum is σ = 32285610. Its totient is φ = 10761868.

The previous prime is 21523727. The next prime is 21523739. The reversal of 21523738 is 83732512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 21464689 + 59049 = 4633^2 + 243^2 .

It is not an unprimeable number, because it can be changed into a prime (21523739) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5380933 + ... + 5380936.

Almost surely, 2^21523738 is an apocalyptic number.

21523738 is a deficient number, since it is larger than the sum of its proper divisors (10761872).

21523738 is a wasteful number, since it uses less digits than its factorization.

21523738 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10761871.

The product of its digits is 10080, while the sum is 31.

The square root of 21523738 is about 4639.3682759617. The cubic root of 21523738 is about 278.1671871872.

The spelling of 21523738 in words is "twenty-one million, five hundred twenty-three thousand, seven hundred thirty-eight".