421216781 has 2 divisors, whose sum is σ = 421216782. Its totient is φ = 421216780.

The previous prime is 421216751. The next prime is 421216787. The reversal of 421216781 is 187612124.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 294294025 + 126922756 = 17155^2 + 11266^2 .

It is a cyclic number.

It is not a de Polignac number, because 421216781 - 2⁶ = 421216717 is a prime.

It is a super-2 number, since 2×421216781² = 354847153192003922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is equal to p_22405829 and since 421216781 and 22405829 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (421216787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 210608390 + 210608391.

It is an arithmetic number, because the mean of its divisors is an integer number (210608391).

Almost surely, 2^421216781 is an apocalyptic number.

It is an amenable number.

421216781 is a deficient number, since it is larger than the sum of its proper divisors (1).

421216781 is an equidigital number, since it uses as much as digits as its factorization.

421216781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5376, while the sum is 32.

The square root of 421216781 is about 20523.5664785631. The cubic root of 421216781 is about 749.6097412623.

The spelling of 421216781 in words is "four hundred twenty-one million, two hundred sixteen thousand, seven hundred eighty-one".