20987820 has 72 divisors (see below), whose sum is σ = 72762144. Its totient is φ = 4796928.

The previous prime is 20987807. The next prime is 20987821. The reversal of 20987820 is 2878902.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (20987821) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7069 + ... + 9588.

Almost surely, 2^20987820 is an apocalyptic number.

20987820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20987820 is an abundant number, since it is smaller than the sum of its proper divisors (51774324).

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

20987820 is a wasteful number, since it uses less digits than its factorization.

20987820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16679 (or 16674 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 36.

The square root of 20987820 is about 4581.2465552511. The cubic root of 20987820 is about 275.8390681218.

The spelling of 20987820 in words is "twenty million, nine hundred eighty-seven thousand, eight hundred twenty".