101821 has 8 divisors (see below), whose sum is σ = 112320. Its totient is φ = 91872.

The previous prime is 101807. The next prime is 101833. The reversal of 101821 is 128101.

101821 = 64² + 65² + ... + 82².

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 101821 - 2⁵ = 101789 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 (101891) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 321 + ... + 553.

It is an arithmetic number, because the mean of its divisors is an integer number (14040).

2¹⁰¹⁸²¹ is an apocalyptic number.

It is an amenable number.

101821 is a deficient number, since it is larger than the sum of its proper divisors (10499).

101821 is a wasteful number, since it uses less digits than its factorization.

101821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 275.

The product of its (nonzero) digits is 16, while the sum is 13.

The square root of 101821 is about 319.0940300288. The cubic root of 101821 is about 46.6959396837.

Adding to 101821 its reverse (128101), we get a palindrome (229922).

The spelling of 101821 in words is "one hundred one thousand, eight hundred twenty-one".