55321991 has 2 divisors, whose sum is σ = 55321992. Its totient is φ = 55321990.

The previous prime is 55321909. The next prime is 55322009. The reversal of 55321991 is 19912355.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-55321991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (55321691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 27660995 + 27660996.

It is an arithmetic number, because the mean of its divisors is an integer number (27660996).

Almost surely, 2^55321991 is an apocalyptic number.

55321991 is a deficient number, since it is larger than the sum of its proper divisors (1).

55321991 is an equidigital number, since it uses as much as digits as its factorization.

55321991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12150, while the sum is 35.

The square root of 55321991 is about 7437.8754359024. The cubic root of 55321991 is about 381.0359337197.

The spelling of 55321991 in words is "fifty-five million, three hundred twenty-one thousand, nine hundred ninety-one".