821965815 has 48 divisors (see below), whose sum is σ = 1560293280. Its totient is φ = 396983040.

The previous prime is 821965811. The next prime is 821965831. The reversal of 821965815 is 518569128.

It is a happy number.

It is not a de Polignac number, because 821965815 - 2² = 821965811 is a prime.

It is a super-2 number, since 2×821965815² = 1351255602057228450, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821965811) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 130069 + ... + 136241.

It is an arithmetic number, because the mean of its divisors is an integer number (32506110).

Almost surely, 2^821965815 is an apocalyptic number.

821965815 is a deficient number, since it is larger than the sum of its proper divisors (738327465).

821965815 is a wasteful number, since it uses less digits than its factorization.

821965815 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6464 (or 6461 counting only the distinct ones).

The product of its digits is 172800, while the sum is 45.

The square root of 821965815 is about 28669.9461980660. The cubic root of 821965815 is about 936.7375261774.

The spelling of 821965815 in words is "eight hundred twenty-one million, nine hundred sixty-five thousand, eight hundred fifteen".