816213997 has 2 divisors, whose sum is σ = 816213998. Its totient is φ = 816213996.

The previous prime is 816213947. The next prime is 816214031. The reversal of 816213997 is 799312618.

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., 640545481 + 175668516 = 25309^2 + 13254^2 .

It is a cyclic number.

It is not a de Polignac number, because 816213997 - 2¹⁵ = 816181229 is a prime.

It is a super-3 number, since 3×816213997³ (a number of 28 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (816213907) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 408106998 + 408106999.

It is an arithmetic number, because the mean of its divisors is an integer number (408106999).

Almost surely, 2^816213997 is an apocalyptic number.

It is an amenable number.

816213997 is a deficient number, since it is larger than the sum of its proper divisors (1).

816213997 is an equidigital number, since it uses as much as digits as its factorization.

816213997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 163296, while the sum is 46.

The square root of 816213997 is about 28569.4591653395. The cubic root of 816213997 is about 934.5474267935.

The spelling of 816213997 in words is "eight hundred sixteen million, two hundred thirteen thousand, nine hundred ninety-seven".