21797724 has 24 divisors (see below), whose sum is σ = 54774160. Its totient is φ = 6706944.

The previous prime is 21797701. The next prime is 21797729. The reversal of 21797724 is 42779712.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21797729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 69709 + ... + 70020.

Almost surely, 2^21797724 is an apocalyptic number.

It is an amenable number.

21797724 is an abundant number, since it is smaller than the sum of its proper divisors (32976436).

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

21797724 is a wasteful number, since it uses less digits than its factorization.

21797724 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 139749 (or 139747 counting only the distinct ones).

The product of its digits is 49392, while the sum is 39.

The square root of 21797724 is about 4668.8032727884. The cubic root of 21797724 is about 279.3425219866.

The spelling of 21797724 in words is "twenty-one million, seven hundred ninety-seven thousand, seven hundred twenty-four".