21372128 has 36 divisors (see below), whose sum is σ = 44716392. Its totient is φ = 10053120.

The previous prime is 21372103. The next prime is 21372133. The reversal of 21372128 is 82127312.

It is a Cunningham number, because it is equal to 4623²-1.

It is a junction number, because it is equal to n+sod(n) for n = 21372097 and 21372106.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 8093 + ... + 10403.

It is an arithmetic number, because the mean of its divisors is an integer number (1242122).

Almost surely, 2^21372128 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 21372128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22358196).

21372128 is an abundant number, since it is smaller than the sum of its proper divisors (23344264).

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

21372128 is a wasteful number, since it uses less digits than its factorization.

21372128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2355 (or 2330 counting only the distinct ones).

The product of its digits is 1344, while the sum is 26.

The square root of 21372128 is about 4622.9998918451. Note that the first 3 decimals coincide. The cubic root of 21372128 is about 277.5125249332.

The spelling of 21372128 in words is "twenty-one million, three hundred seventy-two thousand, one hundred twenty-eight".