21022506 has 96 divisors (see below), whose sum is σ = 52565760. Its totient is φ = 6031872.

The previous prime is 21022471. The next prime is 21022517. The reversal of 21022506 is 60522012.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 204051 + ... + 204153.

It is an arithmetic number, because the mean of its divisors is an integer number (547560).

Almost surely, 2^21022506 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21022506, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26282880).

21022506 is an abundant number, since it is smaller than the sum of its proper divisors (31543254).

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

21022506 is a wasteful number, since it uses less digits than its factorization.

21022506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 180 (or 177 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21022506 is about 4585.0306433000. The cubic root of 21022506 is about 275.9909417317.

Adding to 21022506 its reverse (60522012), we get a palindrome (81544518).

It can be divided in two parts, 21022 and 506, that added together give a triangular number (21528 = T₂₀₇).

The spelling of 21022506 in words is "twenty-one million, twenty-two thousand, five hundred six".