21063781 has 2 divisors, whose sum is σ = 21063782. Its totient is φ = 21063780.

The previous prime is 21063769. The next prime is 21063793. The reversal of 21063781 is 18736012.

It is a balanced prime because it is at equal distance from previous prime (21063769) and next prime (21063793).

It can be written as a sum of positive squares in only one way, i.e., 16402500 + 4661281 = 4050^2 + 2159^2 .

It is a cyclic number.

It is not a de Polignac number, because 21063781 - 2¹³ = 21055589 is a prime.

It is a super-2 number, since 2×21063781² = 887365740031922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21063701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10531890 + 10531891.

It is an arithmetic number, because the mean of its divisors is an integer number (10531891).

Almost surely, 2^21063781 is an apocalyptic number.

21063781 is the 2053-rd centered decagonal number.

It is an amenable number.

21063781 is a deficient number, since it is larger than the sum of its proper divisors (1).

21063781 is an equidigital number, since it uses as much as digits as its factorization.

21063781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 21063781 is about 4589.5294965824. The cubic root of 21063781 is about 276.1714479469.

Adding to 21063781 its reverse (18736012), we get a palindrome (39799793).

The spelling of 21063781 in words is "twenty-one million, sixty-three thousand, seven hundred eighty-one".