21997536 has 96 divisors (see below), whose sum is σ = 64810368. Its totient is φ = 6474240.

The previous prime is 21997531. The next prime is 21997567. The reversal of 21997536 is 63579912.

It is a tau number, because it is divible by the number of its divisors (96).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21997531) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 38791 + ... + 39353.

It is an arithmetic number, because the mean of its divisors is an integer number (675108).

Almost surely, 2^21997536 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 21997536, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32405184).

21997536 is an abundant number, since it is smaller than the sum of its proper divisors (42812832).

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

21997536 is a wasteful number, since it uses less digits than its factorization.

21997536 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 624 (or 616 counting only the distinct ones).

The product of its digits is 102060, while the sum is 42.

The square root of 21997536 is about 4690.1530891859. The cubic root of 21997536 is about 280.1934717281.

The spelling of 21997536 in words is "twenty-one million, nine hundred ninety-seven thousand, five hundred thirty-six".