20857720 has 32 divisors (see below), whose sum is σ = 50541120. Its totient is φ = 7701120.

The previous prime is 20857717. The next prime is 20857721. The reversal of 20857720 is 2775802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20857721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19536 + ... + 20575.

It is an arithmetic number, because the mean of its divisors is an integer number (1579410).

Almost surely, 2^20857720 is an apocalyptic number.

20857720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20857720 is an abundant number, since it is smaller than the sum of its proper divisors (29683400).

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

20857720 is a wasteful number, since it uses less digits than its factorization.

20857720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40135 (or 40131 counting only the distinct ones).

The product of its (nonzero) digits is 7840, while the sum is 31.

The square root of 20857720 is about 4567.0252900548. The cubic root of 20857720 is about 275.2679262087.

The spelling of 20857720 in words is "twenty million, eight hundred fifty-seven thousand, seven hundred twenty".