20021540 has 48 divisors (see below), whose sum is σ = 52424064. Its totient is φ = 6240000.

The previous prime is 20021539. The next prime is 20021549. The reversal of 20021540 is 4512002.

It is a Harshad number since it is a multiple of its sum of digits (14).

It is not an unprimeable number, because it can be changed into a prime (20021549) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4961 + ... + 8040.

It is an arithmetic number, because the mean of its divisors is an integer number (1092168).

Almost surely, 2^20021540 is an apocalyptic number.

20021540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20021540 is an abundant number, since it is smaller than the sum of its proper divisors (32402524).

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

20021540 is a wasteful number, since it uses less digits than its factorization.

20021540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13028 (or 13026 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 14.

The square root of 20021540 is about 4474.5435521403. The cubic root of 20021540 is about 271.5391742892.

Adding to 20021540 its reverse (4512002), we get a palindrome (24533542).

The spelling of 20021540 in words is "twenty million, twenty-one thousand, five hundred forty".