20421560 has 64 divisors (see below), whose sum is σ = 48660480. Its totient is φ = 7701120.

The previous prime is 20421553. The next prime is 20421571. The reversal of 20421560 is 6512402.

It is a happy number.

It is a super-2 number, since 2×20421560² = 834080225667200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 53129 + ... + 53511.

It is an arithmetic number, because the mean of its divisors is an integer number (760320).

Almost surely, 2^20421560 is an apocalyptic number.

20421560 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 20421560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24330240).

20421560 is an abundant number, since it is smaller than the sum of its proper divisors (28238920).

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

20421560 is a wasteful number, since it uses less digits than its factorization.

20421560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 468 (or 464 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 20.

The square root of 20421560 is about 4519.0220180920. The cubic root of 20421560 is about 273.3356665807.

Adding to 20421560 its reverse (6512402), we get a palindrome (26933962).

The spelling of 20421560 in words is "twenty million, four hundred twenty-one thousand, five hundred sixty".