56721821 has 16 divisors (see below), whose sum is σ = 64827840. Its totient is φ = 49196160.

The previous prime is 56721811. The next prime is 56721827. The reversal of 56721821 is 12812765.

It is not a de Polignac number, because 56721821 - 2⁶ = 56721757 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (56721827) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 31481 + ... + 33233.

It is an arithmetic number, because the mean of its divisors is an integer number (4051740).

Almost surely, 2^56721821 is an apocalyptic number.

It is an amenable number.

56721821 is a deficient number, since it is larger than the sum of its proper divisors (8106019).

56721821 is a wasteful number, since it uses less digits than its factorization.

56721821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1916.

The product of its digits is 6720, while the sum is 32.

The square root of 56721821 is about 7531.3890485089. The cubic root of 56721821 is about 384.2230262759.

The spelling of 56721821 in words is "fifty-six million, seven hundred twenty-one thousand, eight hundred twenty-one".