51520021 has 24 divisors (see below), whose sum is σ = 62285496. Its totient is φ = 42456960.

The previous prime is 51520003. The next prime is 51520033. The reversal of 51520021 is 12002515.

It can be written as a sum of positive squares in 4 ways, for example, as 1535121 + 49984900 = 1239^2 + 7070^2 .

It is not a de Polignac number, because 51520021 - 2⁷ = 51519893 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 51519977 and 51520004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51520121) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 284551 + ... + 284731.

It is an arithmetic number, because the mean of its divisors is an integer number (2595229).

Almost surely, 2^51520021 is an apocalyptic number.

It is an amenable number.

51520021 is a deficient number, since it is larger than the sum of its proper divisors (10765475).

51520021 is a wasteful number, since it uses less digits than its factorization.

51520021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 389 (or 382 counting only the distinct ones).

The product of its (nonzero) digits is 100, while the sum is 16.

The square root of 51520021 is about 7177.7448408257. The cubic root of 51520021 is about 372.0991492949.

Adding to 51520021 its reverse (12002515), we get a palindrome (63522536).

The spelling of 51520021 in words is "fifty-one million, five hundred twenty thousand, twenty-one".