864969821 has 2 divisors, whose sum is σ = 864969822. Its totient is φ = 864969820.

The previous prime is 864969803. The next prime is 864969823. The reversal of 864969821 is 128969468.

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., 642064921 + 222904900 = 25339^2 + 14930^2 .

It is a cyclic number.

It is not a de Polignac number, because 864969821 - 2¹⁴ = 864953437 is a prime.

Together with 864969823, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (864969823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 432484910 + 432484911.

It is an arithmetic number, because the mean of its divisors is an integer number (432484911).

Almost surely, 2^864969821 is an apocalyptic number.

It is an amenable number.

864969821 is a deficient number, since it is larger than the sum of its proper divisors (1).

864969821 is an equidigital number, since it uses as much as digits as its factorization.

864969821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1492992, while the sum is 53.

The square root of 864969821 is about 29410.3692768384. The cubic root of 864969821 is about 952.7968624814.

The spelling of 864969821 in words is "eight hundred sixty-four million, nine hundred sixty-nine thousand, eight hundred twenty-one".