51420440 has 16 divisors (see below), whose sum is σ = 115696080. Its totient is φ = 20568160.

The previous prime is 51420419. The next prime is 51420443. The reversal of 51420440 is 4402415.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51420443) 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, 642716 + ... + 642795.

It is an arithmetic number, because the mean of its divisors is an integer number (7231005).

Almost surely, 2^51420440 is an apocalyptic number.

It is an amenable number.

51420440 is an abundant number, since it is smaller than the sum of its proper divisors (64275640).

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

51420440 is a wasteful number, since it uses less digits than its factorization.

51420440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1285522 (or 1285518 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 20.

The square root of 51420440 is about 7170.8046968245. The cubic root of 51420440 is about 371.8592561185.

Adding to 51420440 its reverse (4402415), we get a palindrome (55822855).

The spelling of 51420440 in words is "fifty-one million, four hundred twenty thousand, four hundred forty".