51721660 has 24 divisors (see below), whose sum is σ = 109635120. Its totient is φ = 20494464.

The previous prime is 51721643. The next prime is 51721669. The reversal of 51721660 is 6612715.

It is a super-2 number, since 2×51721660² = 5350260226311200, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51721669) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9945 + ... + 14224.

It is an arithmetic number, because the mean of its divisors is an integer number (4568130).

Almost surely, 2^51721660 is an apocalyptic number.

It is an amenable number.

51721660 is an abundant number, since it is smaller than the sum of its proper divisors (57913460).

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

51721660 is a wasteful number, since it uses less digits than its factorization.

51721660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24285 (or 24283 counting only the distinct ones).

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 51721660 is about 7191.7772490533. Note that the first 3 decimals coincide. The cubic root of 51721660 is about 372.5839577731.

The spelling of 51721660 in words is "fifty-one million, seven hundred twenty-one thousand, six hundred sixty".