21009264 has 20 divisors (see below), whose sum is σ = 54274056. Its totient is φ = 7003072.

The previous prime is 21009217. The next prime is 21009271. The reversal of 21009264 is 46290012.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 218799 + ... + 218894.

Almost surely, 2^21009264 is an apocalyptic number.

21009264 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21009264 is an abundant number, since it is smaller than the sum of its proper divisors (33264792).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21009264 is a wasteful number, since it uses less digits than its factorization.

21009264 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 437704 (or 437698 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 21009264 is about 4583.5863687728. The cubic root of 21009264 is about 275.9329809971.

Adding to 21009264 its reverse (46290012), we get a palindrome (67299276).

The spelling of 21009264 in words is "twenty-one million, nine thousand, two hundred sixty-four".