20990400 has 84 divisors (see below), whose sum is σ = 68881752. Its totient is φ = 5596160.

The previous prime is 20990399. The next prime is 20990423. The reversal of 20990400 is 409902.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2614 + ... + 6986.

Almost surely, 2^20990400 is an apocalyptic number.

20990400 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 20990400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34440876).

20990400 is an abundant number, since it is smaller than the sum of its proper divisors (47891352).

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

20990400 is a wasteful number, since it uses less digits than its factorization.

20990400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4398 (or 4383 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 24.

The square root of 20990400 is about 4581.5281293472. The cubic root of 20990400 is about 275.8503704809.

It can be divided in two parts, 209 and 90400, that added together give a palindrome (90609).

The spelling of 20990400 in words is "twenty million, nine hundred ninety thousand, four hundred".