51121661 has 4 divisors (see below), whose sum is σ = 51207324. Its totient is φ = 51036000.

The previous prime is 51121657. The next prime is 51121717. The reversal of 51121661 is 16612115.

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

It can be written as a sum of positive squares in 2 ways, for example, as 46308025 + 4813636 = 6805^2 + 2194^2 .

It is a cyclic number.

It is not a de Polignac number, because 51121661 - 2² = 51121657 is a prime.

It is a super-2 number, since 2×51121661² = 5226848446797842, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51121061) 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, 41930 + ... + 43131.

It is an arithmetic number, because the mean of its divisors is an integer number (12801831).

Almost surely, 2^51121661 is an apocalyptic number.

It is an amenable number.

51121661 is a deficient number, since it is larger than the sum of its proper divisors (85663).

51121661 is an equidigital number, since it uses as much as digits as its factorization.

51121661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85662.

The product of its digits is 360, while the sum is 23.

The square root of 51121661 is about 7149.9413284306. The cubic root of 51121661 is about 371.1376259404.

Adding to 51121661 its reverse (16612115), we get a palindrome (67733776).

The spelling of 51121661 in words is "fifty-one million, one hundred twenty-one thousand, six hundred sixty-one".