821889749 has 2 divisors, whose sum is σ = 821889750. Its totient is φ = 821889748.

The previous prime is 821889689. The next prime is 821889781. The reversal of 821889749 is 947988128.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 564062500 + 257827249 = 23750^2 + 16057^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-821889749 is a prime.

It is a super-2 number, since 2×821889749² = 1351005519022566002, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 821889694 and 821889703.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (821889349) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410944874 + 410944875.

It is an arithmetic number, because the mean of its divisors is an integer number (410944875).

Almost surely, 2^821889749 is an apocalyptic number.

It is an amenable number.

821889749 is a deficient number, since it is larger than the sum of its proper divisors (1).

821889749 is an equidigital number, since it uses as much as digits as its factorization.

821889749 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2322432, while the sum is 56.

The square root of 821889749 is about 28668.6195865793. The cubic root of 821889749 is about 936.7086295682.

The spelling of 821889749 in words is "eight hundred twenty-one million, eight hundred eighty-nine thousand, seven hundred forty-nine".