20996640 has 144 divisors (see below), whose sum is σ = 81926208. Its totient is φ = 4796928.

The previous prime is 20996621. The next prime is 20996659. The reversal of 20996640 is 4669902.

20996640 is a `hidden beast` number, since 2 + 0 + 9 + 9 + 6 + 640 = 666.

It is an interprime number because it is at equal distance from previous prime (20996621) and next prime (20996659).

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

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 20996595 and 20996604.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 9039 + ... + 11121.

It is an arithmetic number, because the mean of its divisors is an integer number (568932).

Almost surely, 2^20996640 is an apocalyptic number.

20996640 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 20996640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40963104).

20996640 is an abundant number, since it is smaller than the sum of its proper divisors (60929568).

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

20996640 is a wasteful number, since it uses less digits than its factorization.

20996640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2111 (or 2100 counting only the distinct ones).

The product of its (nonzero) digits is 23328, while the sum is 36.

The square root of 20996640 is about 4582.2090742348. The cubic root of 20996640 is about 275.8777025910.

The spelling of 20996640 in words is "twenty million, nine hundred ninety-six thousand, six hundred forty".