21023770 has 16 divisors (see below), whose sum is σ = 38866248. Its totient is φ = 8182080.

The previous prime is 21023767. The next prime is 21023773. The reversal of 21023770 is 7732012.

It is an interprime number because it is at equal distance from previous prime (21023767) and next prime (21023773).

It can be written as a sum of positive squares in 4 ways, for example, as 19193161 + 1830609 = 4381^2 + 1353^2 .

It is not an unprimeable number, because it can be changed into a prime (21023773) 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, 28041 + ... + 28780.

Almost surely, 2^21023770 is an apocalyptic number.

21023770 is a deficient number, since it is larger than the sum of its proper divisors (17842478).

21023770 is a wasteful number, since it uses less digits than its factorization.

21023770 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56865.

The product of its (nonzero) digits is 588, while the sum is 22.

The square root of 21023770 is about 4585.1684810921. The cubic root of 21023770 is about 275.9964730348.

Adding to 21023770 its reverse (7732012), we get a palindrome (28755782).

The spelling of 21023770 in words is "twenty-one million, twenty-three thousand, seven hundred seventy".