21506628 has 96 divisors (see below), whose sum is σ = 60060672. Its totient is φ = 5904000.

The previous prime is 21506627. The next prime is 21506629. The reversal of 21506628 is 82660512.

It is an interprime number because it is at equal distance from previous prime (21506627) and next prime (21506629).

It is a junction number, because it is equal to n+sod(n) for n = 21506595 and 21506604.

It is not an unprimeable number, because it can be changed into a prime (21506627) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 142353 + ... + 142503.

It is an arithmetic number, because the mean of its divisors is an integer number (625632).

Almost surely, 2^21506628 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21506628, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30030336).

21506628 is an abundant number, since it is smaller than the sum of its proper divisors (38554044).

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

21506628 is a wasteful number, since it uses less digits than its factorization.

21506628 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265 (or 263 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 30.

The square root of 21506628 is about 4637.5239082942. The cubic root of 21506628 is about 278.0934592520.

It can be divided in two parts, 2150 and 6628, that added together give a palindrome (8778).

The spelling of 21506628 in words is "twenty-one million, five hundred six thousand, six hundred twenty-eight".