51981091 has 4 divisors (see below), whose sum is σ = 52068184. Its totient is φ = 51894000.

The previous prime is 51981067. The next prime is 51981151. The reversal of 51981091 is 19018915.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19018915 = 5 ⋅3803783.

It is a cyclic number.

It is not a de Polignac number, because 51981091 - 2¹⁹ = 51456803 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51981001) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 42645 + ... + 43846.

It is an arithmetic number, because the mean of its divisors is an integer number (13017046).

Almost surely, 2^51981091 is an apocalyptic number.

51981091 is a deficient number, since it is larger than the sum of its proper divisors (87093).

51981091 is an equidigital number, since it uses as much as digits as its factorization.

51981091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87092.

The product of its (nonzero) digits is 3240, while the sum is 34.

The square root of 51981091 is about 7209.7913284644. The cubic root of 51981091 is about 373.2058678548.

The spelling of 51981091 in words is "fifty-one million, nine hundred eighty-one thousand, ninety-one".