21491744 has 24 divisors (see below), whose sum is σ = 43298640. Its totient is φ = 10495296.

The previous prime is 21491741. The next prime is 21491747. The reversal of 21491744 is 44719412.

It is an interprime number because it is at equal distance from previous prime (21491741) and next prime (21491747).

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a self number, because there is not a number n which added to its sum of digits gives 21491744.

It is not an unprimeable number, because it can be changed into a prime (21491741) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6434 + ... + 9185.

It is an arithmetic number, because the mean of its divisors is an integer number (1804110).

Almost surely, 2^21491744 is an apocalyptic number.

It is an amenable number.

21491744 is an abundant number, since it is smaller than the sum of its proper divisors (21806896).

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

21491744 is a wasteful number, since it uses less digits than its factorization.

21491744 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15672 (or 15664 counting only the distinct ones).

The product of its digits is 8064, while the sum is 32.

The square root of 21491744 is about 4635.9188948902. The cubic root of 21491744 is about 278.0292914636.

The spelling of 21491744 in words is "twenty-one million, four hundred ninety-one thousand, seven hundred forty-four".