21383506 has 4 divisors (see below), whose sum is σ = 32075262. Its totient is φ = 10691752.

The previous prime is 21383503. The next prime is 21383573. The reversal of 21383506 is 60538312.

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., 21242881 + 140625 = 4609^2 + 375^2 .

It is a super-3 number, since 3×21383506³ (a number of 23 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (21383503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5345875 + ... + 5345878.

Almost surely, 2^21383506 is an apocalyptic number.

21383506 is a deficient number, since it is larger than the sum of its proper divisors (10691756).

21383506 is a wasteful number, since it uses less digits than its factorization.

21383506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10691755.

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 21383506 is about 4624.2303143334. The cubic root of 21383506 is about 277.5617631644.

The spelling of 21383506 in words is "twenty-one million, three hundred eighty-three thousand, five hundred six".