1821236221 has 16 divisors (see below), whose sum is σ = 2165673600. Its totient is φ = 1498488768.

The previous prime is 1821236119. The next prime is 1821236227. The reversal of 1821236221 is 1226321281.

It is not a de Polignac number, because 1821236221 - 2¹⁵ = 1821203453 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1821236221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1821236227) 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, 9190 + ... + 61048.

It is an arithmetic number, because the mean of its divisors is an integer number (135354600).

Almost surely, 2^1821236221 is an apocalyptic number.

It is an amenable number.

1821236221 is a deficient number, since it is larger than the sum of its proper divisors (344437379).

1821236221 is a wasteful number, since it uses less digits than its factorization.

1821236221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52068.

The product of its digits is 2304, while the sum is 28.

The square root of 1821236221 is about 42675.9442894941. The cubic root of 1821236221 is about 1221.2055227592.

The spelling of 1821236221 in words is "one billion, eight hundred twenty-one million, two hundred thirty-six thousand, two hundred twenty-one".