1821238661 has 8 divisors (see below), whose sum is σ = 1987395744. Its totient is φ = 1655179920.

The previous prime is 1821238637. The next prime is 1821238663. The reversal of 1821238661 is 1668321281.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1821238661 - 2²² = 1817044357 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1821238663) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17246 + ... + 62768.

It is an arithmetic number, because the mean of its divisors is an integer number (248424468).

Almost surely, 2^1821238661 is an apocalyptic number.

1821238661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1821238661 is a deficient number, since it is larger than the sum of its proper divisors (166157083).

1821238661 is a wasteful number, since it uses less digits than its factorization.

1821238661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49171.

The product of its digits is 27648, while the sum is 38.

The square root of 1821238661 is about 42675.9728770183. The cubic root of 1821238661 is about 1221.2060681287.

The spelling of 1821238661 in words is "one billion, eight hundred twenty-one million, two hundred thirty-eight thousand, six hundred sixty-one".