21523899 has 16 divisors (see below), whose sum is σ = 29646080. Its totient is φ = 13880160.

The previous prime is 21523897. The next prime is 21523907. The reversal of 21523899 is 99832512.

It is not a de Polignac number, because 21523899 - 2¹ = 21523897 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21523891) 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, 22962 + ... + 23880.

It is an arithmetic number, because the mean of its divisors is an integer number (1852880).

Almost surely, 2^21523899 is an apocalyptic number.

21523899 is a deficient number, since it is larger than the sum of its proper divisors (8122181).

21523899 is a wasteful number, since it uses less digits than its factorization.

21523899 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1170.

The product of its digits is 38880, while the sum is 39.

The square root of 21523899 is about 4639.3856274296. The cubic root of 21523899 is about 278.1678807595.

It can be divided in two parts, 21523 and 899, that added together give a palindrome (22422).

The spelling of 21523899 in words is "twenty-one million, five hundred twenty-three thousand, eight hundred ninety-nine".