20451816 has 288 divisors, whose sum is σ = 76826880. Its totient is φ = 4838400.

The previous prime is 20451811. The next prime is 20451839. The reversal of 20451816 is 61815402.

It is a self number, because there is not a number n which added to its sum of digits gives 20451816.

It is not an unprimeable number, because it can be changed into a prime (20451811) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 659721 + ... + 659751.

It is an arithmetic number, because the mean of its divisors is an integer number (266760).

Almost surely, 2^20451816 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20451816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38413440).

20451816 is an abundant number, since it is smaller than the sum of its proper divisors (56375064).

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

20451816 is a wasteful number, since it uses less digits than its factorization.

20451816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85 (or 71 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 20451816 is about 4522.3684060457. The cubic root of 20451816 is about 273.4705887424.

The spelling of 20451816 in words is "twenty million, four hundred fifty-one thousand, eight hundred sixteen".