20217540 has 96 divisors (see below), whose sum is σ = 66495744. Its totient is φ = 4492800.

The previous prime is 20217523. The next prime is 20217557. The reversal of 20217540 is 4571202.

It is an interprime number because it is at equal distance from previous prime (20217523) and next prime (20217557).

It is a Harshad number since it is a multiple of its sum of digits (21).

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 14890 + ... + 16190.

It is an arithmetic number, because the mean of its divisors is an integer number (692664).

Almost surely, 2^20217540 is an apocalyptic number.

20217540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20217540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33247872).

20217540 is an abundant number, since it is smaller than the sum of its proper divisors (46278204).

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

20217540 is a wasteful number, since it uses less digits than its factorization.

20217540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1357 (or 1355 counting only the distinct ones).

The product of its (nonzero) digits is 560, while the sum is 21.

The square root of 20217540 is about 4496.3918868355. The cubic root of 20217540 is about 272.4223721871.

Adding to 20217540 its reverse (4571202), we get a palindrome (24788742).

The spelling of 20217540 in words is "twenty million, two hundred seventeen thousand, five hundred forty".