20781390 has 96 divisors (see below), whose sum is σ = 59163264. Its totient is φ = 4656960.

The previous prime is 20781389. The next prime is 20781403. The reversal of 20781390 is 9318702.

It is a happy number.

It is a super-3 number, since 3×20781390³ (a number of 23 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

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 47 ways as a sum of consecutive naturals, for example, 98385 + ... + 98595.

It is an arithmetic number, because the mean of its divisors is an integer number (616284).

Almost surely, 2^20781390 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20781390, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29581632).

20781390 is an abundant number, since it is smaller than the sum of its proper divisors (38381874).

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

20781390 is a wasteful number, since it uses less digits than its factorization.

20781390 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 302 (or 295 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 30.

The square root of 20781390 is about 4558.6609876147. The cubic root of 20781390 is about 274.9317296093.

The spelling of 20781390 in words is "twenty million, seven hundred eighty-one thousand, three hundred ninety".