21023506 has 8 divisors (see below), whose sum is σ = 36040320. Its totient is φ = 9010068.

The previous prime is 21023503. The next prime is 21023531. The reversal of 21023506 is 60532012.

It is a happy number.

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

It is not an unprimeable number, because it can be changed into a prime (21023501) 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, 750826 + ... + 750853.

It is an arithmetic number, because the mean of its divisors is an integer number (4505040).

Almost surely, 2^21023506 is an apocalyptic number.

21023506 is a deficient number, since it is larger than the sum of its proper divisors (15016814).

21023506 is a wasteful number, since it uses less digits than its factorization.

21023506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1501688.

The product of its (nonzero) digits is 360, while the sum is 19.

The square root of 21023506 is about 4585.1396925285. The cubic root of 21023506 is about 275.9953177810.

Adding to 21023506 its reverse (60532012), we get a palindrome (81555518).

It can be divided in two parts, 210 and 23506, that added together give a square (23716 = 154²).

The spelling of 21023506 in words is "twenty-one million, twenty-three thousand, five hundred six".