21891534 has 48 divisors (see below), whose sum is σ = 53625600. Its totient is φ = 5924016.

The previous prime is 21891511. The next prime is 21891539. The reversal of 21891534 is 43519812.

It is a junction number, because it is equal to n+sod(n) for n = 21891495 and 21891504.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21891539) 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, 3627 + ... + 7545.

It is an arithmetic number, because the mean of its divisors is an integer number (1117200).

Almost surely, 2^21891534 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21891534, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26812800).

21891534 is an abundant number, since it is smaller than the sum of its proper divisors (31734066).

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

21891534 is a wasteful number, since it uses less digits than its factorization.

21891534 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3957 (or 3950 counting only the distinct ones).

The product of its digits is 8640, while the sum is 33.

The square root of 21891534 is about 4678.8389585452. The cubic root of 21891534 is about 279.7426802625.

The spelling of 21891534 in words is "twenty-one million, eight hundred ninety-one thousand, five hundred thirty-four".