51551561 has 4 divisors (see below), whose sum is σ = 51581124. Its totient is φ = 51522000.

The previous prime is 51551557. The next prime is 51551567. The reversal of 51551561 is 16515515.

It is a happy number.

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 6661561 + 44890000 = 2581^2 + 6700^2 .

It is a cyclic number.

It is not a de Polignac number, because 51551561 - 2² = 51551557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51551567) 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, 11990 + ... + 15711.

It is an arithmetic number, because the mean of its divisors is an integer number (12895281).

Almost surely, 2^51551561 is an apocalyptic number.

It is an amenable number.

51551561 is a deficient number, since it is larger than the sum of its proper divisors (29563).

51551561 is a wasteful number, since it uses less digits than its factorization.

51551561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29562.

The product of its digits is 3750, while the sum is 29.

The square root of 51551561 is about 7179.9415735784. The cubic root of 51551561 is about 372.1750654978.

It can be divided in two parts, 515515 and 61, that multiplied together give a triangular number (31446415 = T₇₉₃₀).

The spelling of 51551561 in words is "fifty-one million, five hundred fifty-one thousand, five hundred sixty-one".