21004464 has 80 divisors (see below), whose sum is σ = 59933664. Its totient is φ = 6297600.

The previous prime is 21004463. The next prime is 21004471. The reversal of 21004464 is 46440012.

It is a self number, because there is not a number n which added to its sum of digits gives 21004464.

It is not an unprimeable number, because it can be changed into a prime (21004463) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25174 + ... + 25994.

Almost surely, 2^21004464 is an apocalyptic number.

21004464 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21004464, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29966832).

21004464 is an abundant number, since it is smaller than the sum of its proper divisors (38929200).

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

21004464 is a wasteful number, since it uses less digits than its factorization.

21004464 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 886 (or 880 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 21.

The square root of 21004464 is about 4583.0627314057. The cubic root of 21004464 is about 275.9119652015.

Adding to 21004464 its reverse (46440012), we get a palindrome (67444476).

The spelling of 21004464 in words is "twenty-one million, four thousand, four hundred sixty-four".