20621664 has 144 divisors (see below), whose sum is σ = 68638752. Its totient is φ = 5750784.

The previous prime is 20621609. The next prime is 20621677. The reversal of 20621664 is 46612602.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (144).

It is a super-2 number, since 2×20621664² = 850506052257792, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 106752 + ... + 106944.

It is an arithmetic number, because the mean of its divisors is an integer number (476658).

Almost surely, 2^20621664 is an apocalyptic number.

20621664 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 20621664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34319376).

20621664 is an abundant number, since it is smaller than the sum of its proper divisors (48017088).

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

20621664 is a wasteful number, since it uses less digits than its factorization.

20621664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 269 (or 258 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 20621664 is about 4541.1082347815. The cubic root of 20621664 is about 274.2255411156.

The spelling of 20621664 in words is "twenty million, six hundred twenty-one thousand, six hundred sixty-four".