61639821 has 6 divisors (see below), whose sum is σ = 89035310. Its totient is φ = 41093208.

The previous prime is 61639783. The next prime is 61639843. The reversal of 61639821 is 12893616.

61639821 is a `hidden beast` number, since 616 + 39 + 8 + 2 + 1 = 666.

61639821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 33698025 + 27941796 = 5805^2 + 5286^2 .

It is not a de Polignac number, because 61639821 - 2⁶ = 61639757 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 (61639121) 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 in 5 ways as a sum of consecutive naturals, for example, 3424426 + ... + 3424443.

Almost surely, 2^61639821 is an apocalyptic number.

It is an amenable number.

61639821 is a deficient number, since it is larger than the sum of its proper divisors (27395489).

61639821 is a wasteful number, since it uses less digits than its factorization.

61639821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6848875 (or 6848872 counting only the distinct ones).

The product of its digits is 15552, while the sum is 36.

The square root of 61639821 is about 7851.1031708926. The cubic root of 61639821 is about 395.0212475885.

The spelling of 61639821 in words is "sixty-one million, six hundred thirty-nine thousand, eight hundred twenty-one".