51649891 has 4 divisors (see below), whose sum is σ = 53045872. Its totient is φ = 50253912.

The previous prime is 51649889. The next prime is 51649903. The reversal of 51649891 is 19894615.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 51649891 - 2¹ = 51649889 is a prime.

It is a super-2 number, since 2×51649891² = 5335422480623762, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51649291) 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, 697935 + ... + 698008.

It is an arithmetic number, because the mean of its divisors is an integer number (13261468).

Almost surely, 2^51649891 is an apocalyptic number.

51649891 is a deficient number, since it is larger than the sum of its proper divisors (1395981).

51649891 is a wasteful number, since it uses less digits than its factorization.

51649891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1395980.

The product of its digits is 77760, while the sum is 43.

The square root of 51649891 is about 7186.7858601742. The cubic root of 51649891 is about 372.4115454430.

The spelling of 51649891 in words is "fifty-one million, six hundred forty-nine thousand, eight hundred ninety-one".