51511661 has 4 divisors (see below), whose sum is σ = 52384800. Its totient is φ = 50638524.

The previous prime is 51511657. The next prime is 51511693. The reversal of 51511661 is 16611515.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 51511661 - 2² = 51511657 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 51511661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51511561) 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, 436481 + ... + 436598.

It is an arithmetic number, because the mean of its divisors is an integer number (13096200).

Almost surely, 2^51511661 is an apocalyptic number.

It is an amenable number.

51511661 is a deficient number, since it is larger than the sum of its proper divisors (873139).

51511661 is an equidigital number, since it uses as much as digits as its factorization.

51511661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 873138.

The product of its digits is 900, while the sum is 26.

The square root of 51511661 is about 7177.1624615861. The cubic root of 51511661 is about 372.0790217335.

The spelling of 51511661 in words is "fifty-one million, five hundred eleven thousand, six hundred sixty-one".