20409312 has 144 divisors (see below), whose sum is σ = 67568256. Its totient is φ = 5280000.

The previous prime is 20409283. The next prime is 20409317. The reversal of 20409312 is 21390402.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20409317) 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, 81187 + ... + 81437.

It is an arithmetic number, because the mean of its divisors is an integer number (469224).

Almost surely, 2^20409312 is an apocalyptic number.

20409312 is a gapful number since it is divisible by the number (22) 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 20409312, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33784128).

20409312 is an abundant number, since it is smaller than the sum of its proper divisors (47158944).

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

20409312 is a wasteful number, since it uses less digits than its factorization.

20409312 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 293 (or 274 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 20409312 is about 4517.6666543693. Note that the first 4 decimals coincide. The cubic root of 20409312 is about 273.2810105413.

Adding to 20409312 its reverse (21390402), we get a palindrome (41799714).

The spelling of 20409312 in words is "twenty million, four hundred nine thousand, three hundred twelve".