21721064 has 16 divisors (see below), whose sum is σ = 41049600. Its totient is φ = 10774512.

The previous prime is 21721057. The next prime is 21721067. The reversal of 21721064 is 46012712.

It is a cake number, because a cake can be divided into 21721064 parts by 507 planar cuts.

It is not an unprimeable number, because it can be changed into a prime (21721067) 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, 9674 + ... + 11705.

It is an arithmetic number, because the mean of its divisors is an integer number (2565600).

Almost surely, 2^21721064 is an apocalyptic number.

It is an amenable number.

21721064 is a deficient number, since it is larger than the sum of its proper divisors (19328536).

21721064 is a wasteful number, since it uses less digits than its factorization.

21721064 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21512 (or 21508 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 21721064 is about 4660.5862292205. The cubic root of 21721064 is about 279.0146658786.

Adding to 21721064 its reverse (46012712), we get a palindrome (67733776).

The spelling of 21721064 in words is "twenty-one million, seven hundred twenty-one thousand, sixty-four".