42447781 has 2 divisors, whose sum is σ = 42447782. Its totient is φ = 42447780.

The previous prime is 42447763. The next prime is 42447791. The reversal of 42447781 is 18774424.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 35640900 + 6806881 = 5970^2 + 2609^2 .

It is a cyclic number.

It is not a de Polignac number, because 42447781 - 2¹⁷ = 42316709 is a prime.

It is a super-2 number, since 2×42447781² = 3603628223647922, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 42447781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (42447701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21223890 + 21223891.

It is an arithmetic number, because the mean of its divisors is an integer number (21223891).

Almost surely, 2^42447781 is an apocalyptic number.

It is an amenable number.

42447781 is a deficient number, since it is larger than the sum of its proper divisors (1).

42447781 is an equidigital number, since it uses as much as digits as its factorization.

42447781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 50176, while the sum is 37.

The square root of 42447781 is about 6515.1961597484. The cubic root of 42447781 is about 348.8336166371.

It can be divided in two parts, 424 and 47781, that added together give a triangular number (48205 = T₃₁₀).

The spelling of 42447781 in words is "forty-two million, four hundred forty-seven thousand, seven hundred eighty-one".