1187821 has 2 divisors, whose sum is σ = 1187822. Its totient is φ = 1187820.

The previous prime is 1187819. The next prime is 1187833. The reversal of 1187821 is 1287811.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 617796 + 570025 = 786^2 + 755^2 .

It is a cyclic number.

It is not a de Polignac number, because 1187821 - 2¹ = 1187819 is a prime.

Together with 1187819, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 1187821.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1187801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 593910 + 593911.

It is an arithmetic number, because the mean of its divisors is an integer number (593911).

2^1187821 is an apocalyptic number.

It is an amenable number.

1187821 is a deficient number, since it is larger than the sum of its proper divisors (1).

1187821 is an equidigital number, since it uses as much as digits as its factorization.

1187821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 896, while the sum is 28.

The square root of 1187821 is about 1089.8720108343. The cubic root of 1187821 is about 105.9051304967.

The spelling of 1187821 in words is "one million, one hundred eighty-seven thousand, eight hundred twenty-one".