61821 has 6 divisors (see below), whose sum is σ = 89310. Its totient is φ = 41208.

The previous prime is 61819. The next prime is 61837. The reversal of 61821 is 12816.

It can be written as a sum of positive squares in only one way, i.e., 34596 + 27225 = 186^2 + 165^2 .

It is not a de Polignac number, because 61821 - 2¹ = 61819 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 61794 and 61803.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 61821.

It is not an unprimeable number, because it can be changed into a prime (61861) 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 5 ways as a sum of consecutive naturals, for example, 3426 + ... + 3443.

It is an arithmetic number, because the mean of its divisors is an integer number (14885).

2⁶¹⁸²¹ is an apocalyptic number.

It is an amenable number.

61821 is a deficient number, since it is larger than the sum of its proper divisors (27489).

61821 is a wasteful number, since it uses less digits than its factorization.

61821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6875 (or 6872 counting only the distinct ones).

The product of its digits is 96, while the sum is 18.

The square root of 61821 is about 248.6382914999. The cubic root of 61821 is about 39.5407899950.

The spelling of 61821 in words is "sixty-one thousand, eight hundred twenty-one".