55809991 has 2 divisors, whose sum is σ = 55809992. Its totient is φ = 55809990.

The previous prime is 55809989. The next prime is 55810021. The reversal of 55809991 is 19990855.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 55809991 - 2¹ = 55809989 is a prime.

It is a super-2 number, since 2×55809991² = 6229510190840162, which contains 22 as substring.

Together with 55809989, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (55809911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 27904995 + 27904996.

It is an arithmetic number, because the mean of its divisors is an integer number (27904996).

Almost surely, 2^55809991 is an apocalyptic number.

55809991 is a deficient number, since it is larger than the sum of its proper divisors (1).

55809991 is an equidigital number, since it uses as much as digits as its factorization.

55809991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 145800, while the sum is 46.

The square root of 55809991 is about 7470.6084758874. The cubic root of 55809991 is about 382.1530389245.

The spelling of 55809991 in words is "fifty-five million, eight hundred nine thousand, nine hundred ninety-one".