21738521 has 8 divisors (see below), whose sum is σ = 25422144. Its totient is φ = 18199440.

The previous prime is 21738503. The next prime is 21738539. The reversal of 21738521 is 12583712.

It is an interprime number because it is at equal distance from previous prime (21738503) and next prime (21738539).

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

It is not a de Polignac number, because 21738521 - 2¹⁰ = 21737497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21738551) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 35810 + ... + 36411.

It is an arithmetic number, because the mean of its divisors is an integer number (3177768).

Almost surely, 2^21738521 is an apocalyptic number.

It is an amenable number.

21738521 is a deficient number, since it is larger than the sum of its proper divisors (3683623).

21738521 is an equidigital number, since it uses as much as digits as its factorization.

21738521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72271.

The product of its digits is 3360, while the sum is 29.

The square root of 21738521 is about 4662.4586861440. The cubic root of 21738521 is about 279.0893929537.

The spelling of 21738521 in words is "twenty-one million, seven hundred thirty-eight thousand, five hundred twenty-one".