816487921 has 4 divisors (see below), whose sum is σ = 820357744. Its totient is φ = 812618100.

The previous prime is 816487909. The next prime is 816487933. The reversal of 816487921 is 129784618.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (816487909) and next prime (816487933).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-816487921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (816487421) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1934595 + ... + 1935016.

It is an arithmetic number, because the mean of its divisors is an integer number (205089436).

Almost surely, 2^816487921 is an apocalyptic number.

It is an amenable number.

816487921 is a deficient number, since it is larger than the sum of its proper divisors (3869823).

816487921 is a wasteful number, since it uses less digits than its factorization.

816487921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3869822.

The product of its digits is 193536, while the sum is 46.

The square root of 816487921 is about 28574.2527636332. The cubic root of 816487921 is about 934.6519607915.

The spelling of 816487921 in words is "eight hundred sixteen million, four hundred eighty-seven thousand, nine hundred twenty-one".