21997392 has 40 divisors (see below), whose sum is σ = 57555840. Its totient is φ = 7238400.

The previous prime is 21997387. The next prime is 21997397. The reversal of 21997392 is 29379912.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21997387) and next prime (21997397).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21997397) 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, 892 + ... + 6692.

It is an arithmetic number, because the mean of its divisors is an integer number (1438896).

Almost surely, 2^21997392 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 21997392, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28777920).

21997392 is an abundant number, since it is smaller than the sum of its proper divisors (35558448).

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

21997392 is a wasteful number, since it uses less digits than its factorization.

21997392 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5891 (or 5885 counting only the distinct ones).

The product of its digits is 61236, while the sum is 42.

The square root of 21997392 is about 4690.1377378495. The cubic root of 21997392 is about 280.1928603271.

It can be divided in two parts, 2199 and 7392, that added together give a triangular number (9591 = T₁₃₈).

The spelling of 21997392 in words is "twenty-one million, nine hundred ninety-seven thousand, three hundred ninety-two".