20751680 has 28 divisors (see below), whose sum is σ = 49415700. Its totient is φ = 8300544.

The previous prime is 20751631. The next prime is 20751683. The reversal of 20751680 is 8615702.

It can be written as a sum of positive squares in 2 ways, for example, as 8248384 + 12503296 = 2872^2 + 3536^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20751683) 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, 32105 + ... + 32744.

Almost surely, 2^20751680 is an apocalyptic number.

20751680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20751680 is an abundant number, since it is smaller than the sum of its proper divisors (28664020).

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

20751680 is an equidigital number, since it uses as much as digits as its factorization.

20751680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64866 (or 64856 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 29.

The square root of 20751680 is about 4555.4011897966. The cubic root of 20751680 is about 274.8006489111.

The spelling of 20751680 in words is "twenty million, seven hundred fifty-one thousand, six hundred eighty".