20724640 has 24 divisors (see below), whose sum is σ = 48962340. Its totient is φ = 8289792.

The previous prime is 20724637. The next prime is 20724653. The reversal of 20724640 is 4642702.

It can be written as a sum of positive squares in 2 ways, for example, as 20466576 + 258064 = 4524^2 + 508^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64605 + ... + 64924.

Almost surely, 2^20724640 is an apocalyptic number.

20724640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20724640 is an abundant number, since it is smaller than the sum of its proper divisors (28237700).

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

20724640 is a wasteful number, since it uses less digits than its factorization.

20724640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129544 (or 129536 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 25.

The square root of 20724640 is about 4552.4323169049. The cubic root of 20724640 is about 274.6812394736.

The spelling of 20724640 in words is "twenty million, seven hundred twenty-four thousand, six hundred forty".