51515991 has 6 divisors (see below), whose sum is σ = 74412000. Its totient is φ = 34343988.

The previous prime is 51515983. The next prime is 51515999. The reversal of 51515991 is 19951515.

51515991 is a `hidden beast` number, since 51 + 515 + 9 + 91 = 666.

It is an interprime number because it is at equal distance from previous prime (51515983) and next prime (51515999).

It is not a de Polignac number, because 51515991 - 2³ = 51515983 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51515999) 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 5 ways as a sum of consecutive naturals, for example, 2861991 + ... + 2862008.

It is an arithmetic number, because the mean of its divisors is an integer number (12402000).

Almost surely, 2^51515991 is an apocalyptic number.

51515991 is a deficient number, since it is larger than the sum of its proper divisors (22896009).

51515991 is a wasteful number, since it uses less digits than its factorization.

51515991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5724005 (or 5724002 counting only the distinct ones).

The product of its digits is 10125, while the sum is 36.

The square root of 51515991 is about 7177.4641064933. The cubic root of 51515991 is about 372.0894469265.

The spelling of 51515991 in words is "fifty-one million, five hundred fifteen thousand, nine hundred ninety-one".