55721428 has 18 divisors (see below), whose sum is σ = 113433306. Its totient is φ = 23880528.

The previous prime is 55721423. The next prime is 55721437. The reversal of 55721428 is 82412755.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 41113744 + 14607684 = 6412^2 + 3822^2 .

It is a super-4 number, since 4×55721428⁴ (a number of 32 digits) contains 4444 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 55721393 and 55721402.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (55721423) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 141951 + ... + 142342.

Almost surely, 2^55721428 is an apocalyptic number.

It is an amenable number.

55721428 is an abundant number, since it is smaller than the sum of its proper divisors (57711878).

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

55721428 is a wasteful number, since it uses less digits than its factorization.

55721428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 284311 (or 284302 counting only the distinct ones).

The product of its digits is 22400, while the sum is 34.

The square root of 55721428 is about 7464.6786936880. The cubic root of 55721428 is about 381.9507899659.

The spelling of 55721428 in words is "fifty-five million, seven hundred twenty-one thousand, four hundred twenty-eight".