21243770 has 8 divisors (see below), whose sum is σ = 38238804. Its totient is φ = 8497504.

The previous prime is 21243769. The next prime is 21243779. The reversal of 21243770 is 7734212.

It can be written as a sum of positive squares in 2 ways, for example, as 21224449 + 19321 = 4607^2 + 139^2 .

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 (21243779) 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, 1062179 + ... + 1062198.

Almost surely, 2^21243770 is an apocalyptic number.

21243770 is a deficient number, since it is larger than the sum of its proper divisors (16995034).

21243770 is a wasteful number, since it uses less digits than its factorization.

21243770 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2124384.

The product of its (nonzero) digits is 2352, while the sum is 26.

The square root of 21243770 is about 4609.0964407354. The cubic root of 21243770 is about 276.9558419011.

Adding to 21243770 its reverse (7734212), we get a palindrome (28977982).

The spelling of 21243770 in words is "twenty-one million, two hundred forty-three thousand, seven hundred seventy".