21205154 has 8 divisors (see below), whose sum is σ = 33678828. Its totient is φ = 9978880.

The previous prime is 21205139. The next prime is 21205157. The reversal of 21205154 is 45150212.

It can be written as a sum of positive squares in 2 ways, for example, as 17682025 + 3523129 = 4205^2 + 1877^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21205157) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 311807 + ... + 311874.

Almost surely, 2^21205154 is an apocalyptic number.

21205154 is a deficient number, since it is larger than the sum of its proper divisors (12473674).

21205154 is a wasteful number, since it uses less digits than its factorization.

21205154 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 623700.

The product of its (nonzero) digits is 400, while the sum is 20.

The square root of 21205154 is about 4604.9054279105. The cubic root of 21205154 is about 276.7879273611.

Adding to 21205154 its reverse (45150212), we get a palindrome (66355366).

The spelling of 21205154 in words is "twenty-one million, two hundred five thousand, one hundred fifty-four".