51199991 has 2 divisors, whose sum is σ = 51199992. Its totient is φ = 51199990.

The previous prime is 51199987. The next prime is 51200027. The reversal of 51199991 is 19999115.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 51199991 - 2² = 51199987 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51199921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25599995 + 25599996.

It is an arithmetic number, because the mean of its divisors is an integer number (25599996).

Almost surely, 2^51199991 is an apocalyptic number.

51199991 is a deficient number, since it is larger than the sum of its proper divisors (1).

51199991 is an equidigital number, since it uses as much as digits as its factorization.

51199991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 32805, while the sum is 44.

The square root of 51199991 is about 7155.4168991052. The cubic root of 51199991 is about 371.3270849316.

The spelling of 51199991 in words is "fifty-one million, one hundred ninety-nine thousand, nine hundred ninety-one".