21557028460 has 72 divisors (see below), whose sum is σ = 50818299840. Its totient is φ = 7672093440.

The previous prime is 21557028457. The next prime is 21557028463. The reversal of 21557028460 is 6482075512.

It is an interprime number because it is at equal distance from previous prime (21557028457) and next prime (21557028463).

It is not an unprimeable number, because it can be changed into a prime (21557028463) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 18976 + ... + 208504.

It is an arithmetic number, because the mean of its divisors is an integer number (705809720).

Almost surely, 2^21557028460 is an apocalyptic number.

21557028460 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21557028460, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25409149920).

21557028460 is an abundant number, since it is smaller than the sum of its proper divisors (29261271380).

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

21557028460 is a wasteful number, since it uses less digits than its factorization.

21557028460 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 189607 (or 189594 counting only the distinct ones).

The product of its (nonzero) digits is 134400, while the sum is 40.

The spelling of 21557028460 in words is "twenty-one billion, five hundred fifty-seven million, twenty-eight thousand, four hundred sixty".