51261640 has 16 divisors (see below), whose sum is σ = 115338780. Its totient is φ = 20504640.

The previous prime is 51261629. The next prime is 51261643. The reversal of 51261640 is 4616215.

It can be written as a sum of positive squares in 2 ways, for example, as 50722884 + 538756 = 7122^2 + 734^2 .

It is not an unprimeable number, because it can be changed into a prime (51261643) 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, 640731 + ... + 640810.

Almost surely, 2^51261640 is an apocalyptic number.

It is an amenable number.

51261640 is an abundant number, since it is smaller than the sum of its proper divisors (64077140).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

51261640 is a wasteful number, since it uses less digits than its factorization.

51261640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1281552 (or 1281548 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 51261640 is about 7159.7234583467. The cubic root of 51261640 is about 371.4760612707.

Adding to 51261640 its reverse (4616215), we get a palindrome (55877855).

It can be divided in two parts, 512616 and 40, that added together give a square (512656 = 716²).

The spelling of 51261640 in words is "fifty-one million, two hundred sixty-one thousand, six hundred forty".