20761781 has 2 divisors, whose sum is σ = 20761782. Its totient is φ = 20761780.

The previous prime is 20761771. The next prime is 20761787. The reversal of 20761781 is 18716702.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19439281 + 1322500 = 4409^2 + 1150^2 .

It is a cyclic number.

It is not a de Polignac number, because 20761781 - 2⁶ = 20761717 is a prime.

It is a super-2 number, since 2×20761781² = 862103100583922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20761787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10380890 + 10380891.

It is an arithmetic number, because the mean of its divisors is an integer number (10380891).

Almost surely, 2^20761781 is an apocalyptic number.

It is an amenable number.

20761781 is a deficient number, since it is larger than the sum of its proper divisors (1).

20761781 is an equidigital number, since it uses as much as digits as its factorization.

20761781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4704, while the sum is 32.

The square root of 20761781 is about 4556.5097388242. The cubic root of 20761781 is about 274.8452286127.

The spelling of 20761781 in words is "twenty million, seven hundred sixty-one thousand, seven hundred eighty-one".