21121744 has 60 divisors (see below), whose sum is σ = 49299300. Its totient is φ = 8730624.

The previous prime is 21121741. The next prime is 21121759. The reversal of 21121744 is 44712112.

It can be written as a sum of positive squares in 2 ways, for example, as 4410000 + 16711744 = 2100^2 + 4088^2 .

It is a super-2 number, since 2×21121744² = 892256139203072, which contains 22 as substring.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121741) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 22272 + ... + 23200.

It is an arithmetic number, because the mean of its divisors is an integer number (821655).

Almost surely, 2^21121744 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 21121744, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24649650).

21121744 is an abundant number, since it is smaller than the sum of its proper divisors (28177556).

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

21121744 is a wasteful number, since it uses less digits than its factorization.

21121744 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 980 (or 967 counting only the distinct ones).

The product of its digits is 448, while the sum is 22.

The square root of 21121744 is about 4595.8398579585. The cubic root of 21121744 is about 276.4245374368.

Adding to 21121744 its reverse (44712112), we get a palindrome (65833856).

The spelling of 21121744 in words is "twenty-one million, one hundred twenty-one thousand, seven hundred forty-four".