20256640 has 64 divisors (see below), whose sum is σ = 50037120. Its totient is φ = 7833600.

The previous prime is 20256637. The next prime is 20256659. The reversal of 20256640 is 4665202.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19330 + ... + 20350.

It is an arithmetic number, because the mean of its divisors is an integer number (781830).

Almost surely, 2^20256640 is an apocalyptic number.

20256640 is a gapful number since it is divisible by the number (20) 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 20256640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25018560).

20256640 is an abundant number, since it is smaller than the sum of its proper divisors (29780480).

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

20256640 is a wasteful number, since it uses less digits than its factorization.

20256640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1071 (or 1059 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 25.

The square root of 20256640 is about 4500.7377173081. The cubic root of 20256640 is about 272.5978774734.

The spelling of 20256640 in words is "twenty million, two hundred fifty-six thousand, six hundred forty".