21534444 has 96 divisors (see below), whose sum is σ = 60903360. Its totient is φ = 6552576.

The previous prime is 21534437. The next prime is 21534451. The reversal of 21534444 is 44443512.

It is a happy number.

21534444 is a `hidden beast` number, since 215 + 3 + 4 + 444 = 666.

It is an interprime number because it is at equal distance from previous prime (21534437) and next prime (21534451).

It is a Harshad number since it is a multiple of its sum of digits (27).

Its product of digits (7680) is a multiple of the sum of its prime factors (384).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 67774 + ... + 68090.

It is an arithmetic number, because the mean of its divisors is an integer number (634410).

Almost surely, 2^21534444 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 21534444, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30451680).

21534444 is an abundant number, since it is smaller than the sum of its proper divisors (39368916).

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

21534444 is a wasteful number, since it uses less digits than its factorization.

21534444 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 384 (or 376 counting only the distinct ones).

The product of its digits is 7680, while the sum is 27.

The square root of 21534444 is about 4640.5219534014. The cubic root of 21534444 is about 278.2133000615.

Adding to 21534444 its reverse (44443512), we get a palindrome (65977956).

The spelling of 21534444 in words is "twenty-one million, five hundred thirty-four thousand, four hundred forty-four".