21243790 has 16 divisors (see below), whose sum is σ = 38476368. Its totient is φ = 8444736.

The previous prime is 21243779. The next prime is 21243793. The reversal of 21243790 is 9734212.

It is a super-2 number, since 2×21243790² = 902597227128200, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21243793) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4887 + ... + 8146.

It is an arithmetic number, because the mean of its divisors is an integer number (2404773).

Almost surely, 2^21243790 is an apocalyptic number.

21243790 is a deficient number, since it is larger than the sum of its proper divisors (17232578).

21243790 is a wasteful number, since it uses less digits than its factorization.

21243790 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13203.

The product of its (nonzero) digits is 3024, while the sum is 28.

The square root of 21243790 is about 4609.0986103576. The cubic root of 21243790 is about 276.9559288147.

The spelling of 21243790 in words is "twenty-one million, two hundred forty-three thousand, seven hundred ninety".