21157444 has 48 divisors (see below), whose sum is σ = 46843776. Its totient is φ = 8121600.

The previous prime is 21157439. The next prime is 21157453. The reversal of 21157444 is 44475112.

It is a super-2 number, since 2×21157444² = 895274873226272, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22014 + ... + 22954.

It is an arithmetic number, because the mean of its divisors is an integer number (975912).

Almost surely, 2^21157444 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 21157444, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23421888).

21157444 is an abundant number, since it is smaller than the sum of its proper divisors (25686332).

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

21157444 is a wasteful number, since it uses less digits than its factorization.

21157444 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1036 (or 1034 counting only the distinct ones).

The product of its digits is 4480, while the sum is 28.

The square root of 21157444 is about 4599.7221655226. The cubic root of 21157444 is about 276.5801874842.

It can be divided in two parts, 2115 and 7444, that added together give a palindrome (9559).

The spelling of 21157444 in words is "twenty-one million, one hundred fifty-seven thousand, four hundred forty-four".