21820552728 has 32 divisors (see below), whose sum is σ = 58747642800. Its totient is φ = 6714016128.

The previous prime is 21820552727. The next prime is 21820552729. The reversal of 21820552728 is 82725502812.

It is an interprime number because it is at equal distance from previous prime (21820552727) and next prime (21820552729).

It is a super-2 number, since 2×21820552728² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21820552728.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21820552727) 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, 34968523 + ... + 34969146.

Almost surely, 2^21820552728 is an apocalyptic number.

It is an amenable number.

21820552728 is an abundant number, since it is smaller than the sum of its proper divisors (36927090072).

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

21820552728 is a wasteful number, since it uses less digits than its factorization.

21820552728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69937691 (or 69937687 counting only the distinct ones).

The product of its (nonzero) digits is 179200, while the sum is 42.

The spelling of 21820552728 in words is "twenty-one billion, eight hundred twenty million, five hundred fifty-two thousand, seven hundred twenty-eight".