51990840225 has 81 divisors (see below), whose sum is σ = 96870109843. Its totient is φ = 27679196880.

The previous prime is 51990840157. The next prime is 51990840241. The reversal of 51990840225 is 52204809915.

It is a happy number.

The square root of 51990840225 is 228015.

It is a perfect power (a square), and thus also a powerful number.

51990840225 is a `hidden beast` number, since 519 + 90 + 8 + 40 + 2 + 2 + 5 = 666.

It can be written as a sum of positive squares in only one way, i.e., 18716702481 + 33274137744 = 136809^2 + 182412^2 .

It is a tau number, because it is divible by the number of its divisors (81).

It is not a de Polignac number, because 51990840225 - 2¹¹ = 51990838177 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 92345794 + ... + 92346356.

Almost surely, 2^51990840225 is an apocalyptic number.

51990840225 is the 228015-th square number.

51990840225 is the 114008-th centered octagonal number.

It is an amenable number.

51990840225 is a deficient number, since it is larger than the sum of its proper divisors (44879269618).

51990840225 is an frugal number, since it uses more digits than its factorization.

51990840225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1160 (or 571 counting only the distinct ones).

The product of its (nonzero) digits is 259200, while the sum is 45.

The spelling of 51990840225 in words is "fifty-one billion, nine hundred ninety million, eight hundred forty thousand, two hundred twenty-five".