20781311 has 2 divisors, whose sum is σ = 20781312. Its totient is φ = 20781310.

The previous prime is 20781287. The next prime is 20781329. The reversal of 20781311 is 11318702.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20781311 - 2¹⁴ = 20764927 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20789311) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10390655 + 10390656.

It is an arithmetic number, because the mean of its divisors is an integer number (10390656).

Almost surely, 2^20781311 is an apocalyptic number.

20781311 is a deficient number, since it is larger than the sum of its proper divisors (1).

20781311 is an equidigital number, since it uses as much as digits as its factorization.

20781311 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 336, while the sum is 23.

The square root of 20781311 is about 4558.6523227814. The cubic root of 20781311 is about 274.9313812266.

It can be divided in two parts, 207 and 81311, that added together give a palindrome (81518).

The spelling of 20781311 in words is "twenty million, seven hundred eighty-one thousand, three hundred eleven".