61638921 has 8 divisors (see below), whose sum is σ = 91316960. Its totient is φ = 41092596.

The previous prime is 61638877. The next prime is 61638931. The reversal of 61638921 is 12983616.

61638921 is a `hidden beast` number, since 616 + 38 + 9 + 2 + 1 = 666.

It is not a de Polignac number, because 61638921 - 2¹⁰ = 61637897 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (61638931) 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, 1141435 + ... + 1141488.

It is an arithmetic number, because the mean of its divisors is an integer number (11414620).

Almost surely, 2^61638921 is an apocalyptic number.

It is an amenable number.

61638921 is a deficient number, since it is larger than the sum of its proper divisors (29678039).

61638921 is a wasteful number, since it uses less digits than its factorization.

61638921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2282932 (or 2282926 counting only the distinct ones).

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

The square root of 61638921 is about 7851.0458538974. The cubic root of 61638921 is about 395.0193250172.

The spelling of 61638921 in words is "sixty-one million, six hundred thirty-eight thousand, nine hundred twenty-one".