21643004 has 6 divisors (see below), whose sum is σ = 37875264. Its totient is φ = 10821500.

The previous prime is 21642979. The next prime is 21643009. The reversal of 21643004 is 40034612.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21643009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2705372 + ... + 2705379.

It is an arithmetic number, because the mean of its divisors is an integer number (6312544).

Almost surely, 2^21643004 is an apocalyptic number.

It is an amenable number.

21643004 is a deficient number, since it is larger than the sum of its proper divisors (16232260).

21643004 is a wasteful number, since it uses less digits than its factorization.

21643004 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5410755 (or 5410753 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 20.

The square root of 21643004 is about 4652.2042087595. The cubic root of 21643004 is about 278.6800286881.

Adding to 21643004 its reverse (40034612), we get a palindrome (61677616).

The spelling of 21643004 in words is "twenty-one million, six hundred forty-three thousand, four".