21505066 has 32 divisors (see below), whose sum is σ = 37428480. Its totient is φ = 9172800.

The previous prime is 21505063. The next prime is 21505109. The reversal of 21505066 is 66050512.

It is a self number, because there is not a number n which added to its sum of digits gives 21505066.

It is not an unprimeable number, because it can be changed into a prime (21505063) 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, 23151 + ... + 24061.

It is an arithmetic number, because the mean of its divisors is an integer number (1169640).

Almost surely, 2^21505066 is an apocalyptic number.

21505066 is a deficient number, since it is larger than the sum of its proper divisors (15923414).

21505066 is a wasteful number, since it uses less digits than its factorization.

21505066 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 990.

The product of its (nonzero) digits is 1800, while the sum is 25.

The square root of 21505066 is about 4637.3554964009. The cubic root of 21505066 is about 278.0867265601.

Adding to 21505066 its reverse (66050512), we get a palindrome (87555578).

It can be divided in two parts, 2150506 and 6, that added together give a palindrome (2150512).

The spelling of 21505066 in words is "twenty-one million, five hundred five thousand, sixty-six".