21239748 has 18 divisors (see below), whose sum is σ = 53689454. Its totient is φ = 7079904.

The previous prime is 21239731. The next prime is 21239753. The reversal of 21239748 is 84793212.

It can be written as a sum of positive squares in only one way, i.e., 21233664 + 6084 = 4608^2 + 78^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a super-2 number, since 2×21239748² = 902253790207008, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 589993 = 21239748 / (2 + 1 + 2 + 3 + 9 + 7 + 4 + 8).

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 294961 + ... + 295032.

Almost surely, 2^21239748 is an apocalyptic number.

It is an amenable number.

21239748 is an abundant number, since it is smaller than the sum of its proper divisors (32449706).

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

21239748 is a wasteful number, since it uses less digits than its factorization.

21239748 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 590003 (or 589998 counting only the distinct ones).

The product of its digits is 24192, while the sum is 36.

The square root of 21239748 is about 4608.6601089688. The cubic root of 21239748 is about 276.9383624753.

The spelling of 21239748 in words is "twenty-one million, two hundred thirty-nine thousand, seven hundred forty-eight".