406216781 has 2 divisors, whose sum is σ = 406216782. Its totient is φ = 406216780.

The previous prime is 406216709. The next prime is 406216799. The reversal of 406216781 is 187612604.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 260531881 + 145684900 = 16141^2 + 12070^2 .

It is a cyclic number.

It is not a de Polignac number, because 406216781 - 2²⁶ = 339107917 is a prime.

It is a super-2 number, since 2×406216781² = 330024146332003922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (406213781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 203108390 + 203108391.

It is an arithmetic number, because the mean of its divisors is an integer number (203108391).

Almost surely, 2^406216781 is an apocalyptic number.

It is an amenable number.

406216781 is a deficient number, since it is larger than the sum of its proper divisors (1).

406216781 is an equidigital number, since it uses as much as digits as its factorization.

406216781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16128, while the sum is 35.

The square root of 406216781 is about 20154.8202919302. The cubic root of 406216781 is about 740.6038296476.

The spelling of 406216781 in words is "four hundred six million, two hundred sixteen thousand, seven hundred eighty-one".