20557720 has 16 divisors (see below), whose sum is σ = 46254960. Its totient is φ = 8223072.

The previous prime is 20557711. The next prime is 20557721. The reversal of 20557720 is 2775502.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20557721) 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, 256932 + ... + 257011.

It is an arithmetic number, because the mean of its divisors is an integer number (2890935).

Almost surely, 2^20557720 is an apocalyptic number.

20557720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20557720 is an abundant number, since it is smaller than the sum of its proper divisors (25697240).

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

20557720 is a wasteful number, since it uses less digits than its factorization.

20557720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 513954 (or 513950 counting only the distinct ones).

The product of its (nonzero) digits is 4900, while the sum is 28.

The square root of 20557720 is about 4534.0621963092. The cubic root of 20557720 is about 273.9418065983.

The spelling of 20557720 in words is "twenty million, five hundred fifty-seven thousand, seven hundred twenty".