816778641 has 16 divisors (see below), whose sum is σ = 1245441024. Its totient is φ = 466420944.

The previous prime is 816778637. The next prime is 816778657. The reversal of 816778641 is 146877618.

It is not a de Polignac number, because 816778641 - 2² = 816778637 is a prime.

It is not an unprimeable number, because it can be changed into a prime (816778661) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21646 + ... + 45848.

It is an arithmetic number, because the mean of its divisors is an integer number (77840064).

Almost surely, 2^816778641 is an apocalyptic number.

It is an amenable number.

816778641 is a deficient number, since it is larger than the sum of its proper divisors (428662383).

816778641 is a wasteful number, since it uses less digits than its factorization.

816778641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25820.

The product of its digits is 451584, while the sum is 48.

The square root of 816778641 is about 28579.3394080409. The cubic root of 816778641 is about 934.7628788539.

The spelling of 816778641 in words is "eight hundred sixteen million, seven hundred seventy-eight thousand, six hundred forty-one".