21205998 has 24 divisors (see below), whose sum is σ = 50123736. Its totient is φ = 6426000.

The previous prime is 21205993. The next prime is 21205999. The reversal of 21205998 is 89950212.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21205991) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 53353 + ... + 53748.

It is an arithmetic number, because the mean of its divisors is an integer number (2088489).

Almost surely, 2^21205998 is an apocalyptic number.

21205998 is an abundant number, since it is smaller than the sum of its proper divisors (28917738).

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

21205998 is a wasteful number, since it uses less digits than its factorization.

21205998 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 107120 (or 107117 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 36.

The square root of 21205998 is about 4604.9970684030. The cubic root of 21205998 is about 276.7915995173.

It can be divided in two parts, 2120 and 5998, that added together give a palindrome (8118).

The spelling of 21205998 in words is "twenty-one million, two hundred five thousand, nine hundred ninety-eight".