20722640 has 20 divisors (see below), whose sum is σ = 48180324. Its totient is φ = 8289024.

The previous prime is 20722621. The next prime is 20722649. The reversal of 20722640 is 4622702.

It can be written as a sum of positive squares in 2 ways, for example, as 7268416 + 13454224 = 2696^2 + 3668^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20722649) 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, 129437 + ... + 129596.

Almost surely, 2^20722640 is an apocalyptic number.

20722640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20722640 is an abundant number, since it is smaller than the sum of its proper divisors (27457684).

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

20722640 is a wasteful number, since it uses less digits than its factorization.

20722640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 259046 (or 259040 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 23.

The square root of 20722640 is about 4552.2126488116. The cubic root of 20722640 is about 274.6724032903.

The spelling of 20722640 in words is "twenty million, seven hundred twenty-two thousand, six hundred forty".