20781028 has 12 divisors (see below), whose sum is σ = 36414252. Its totient is φ = 10376960.

The previous prime is 20781017. The next prime is 20781031. The reversal of 20781028 is 82018702.

It can be written as a sum of positive squares in 2 ways, for example, as 11888704 + 8892324 = 3448^2 + 2982^2 .

It is a super-2 number, since 2×20781028² = 863702249473568, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 20780987 and 20781005.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 576 + ... + 6472.

It is an arithmetic number, because the mean of its divisors is an integer number (3034521).

Almost surely, 2^20781028 is an apocalyptic number.

It is an amenable number.

20781028 is a deficient number, since it is larger than the sum of its proper divisors (15633224).

20781028 is a wasteful number, since it uses less digits than its factorization.

20781028 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6782 (or 6780 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 28.

The square root of 20781028 is about 4558.6212828003. The cubic root of 20781028 is about 274.9301332153.

The spelling of 20781028 in words is "twenty million, seven hundred eighty-one thousand, twenty-eight".