640000020 has 96 divisors (see below), whose sum is σ = 2069940096. Its totient is φ = 146022400.

The previous prime is 640000019. The next prime is 640000027. The reversal of 640000020 is 20000046.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a junction number, because it is equal to n+sod(n) for n = 639999960 and 640000005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640000027) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 17301 + ... + 39740.

It is an arithmetic number, because the mean of its divisors is an integer number (21561876).

Almost surely, 2^640000020 is an apocalyptic number.

640000020 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

640000020 is an abundant number, since it is smaller than the sum of its proper divisors (1429940076).

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

640000020 is a wasteful number, since it uses less digits than its factorization.

640000020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57081 (or 57079 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 12.

The square root of 640000020 is about 25298.2216766317. The cubic root of 640000020 is about 861.7738849896.

640000020 divided by its sum of digits (12) gives a palindrome (53333335).

Adding to 640000020 its reverse (20000046), we get a palindrome (660000066).

The spelling of 640000020 in words is "six hundred forty million, twenty", and thus it is an aban number.