61638491 has 2 divisors, whose sum is σ = 61638492. Its totient is φ = 61638490.

The previous prime is 61638461. The next prime is 61638497. The reversal of 61638491 is 19483616.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 61638491 - 2¹⁸ = 61376347 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (61638497) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30819245 + 30819246.

It is an arithmetic number, because the mean of its divisors is an integer number (30819246).

Almost surely, 2^61638491 is an apocalyptic number.

61638491 is a deficient number, since it is larger than the sum of its proper divisors (1).

61638491 is an equidigital number, since it uses as much as digits as its factorization.

61638491 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 31104, while the sum is 38.

The square root of 61638491 is about 7851.0184689631. The cubic root of 61638491 is about 395.0184064488.

The spelling of 61638491 in words is "sixty-one million, six hundred thirty-eight thousand, four hundred ninety-one".