21523798 has 4 divisors (see below), whose sum is σ = 32285700. Its totient is φ = 10761898.

The previous prime is 21523793. The next prime is 21523813. The reversal of 21523798 is 89732512.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523793) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5380948 + ... + 5380951.

It is an arithmetic number, because the mean of its divisors is an integer number (8071425).

Almost surely, 2^21523798 is an apocalyptic number.

21523798 is a deficient number, since it is larger than the sum of its proper divisors (10761902).

21523798 is a wasteful number, since it uses less digits than its factorization.

21523798 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10761901.

The product of its digits is 30240, while the sum is 37.

The square root of 21523798 is about 4639.3747423548. The cubic root of 21523798 is about 278.1674456618.

The spelling of 21523798 in words is "twenty-one million, five hundred twenty-three thousand, seven hundred ninety-eight".