21505010 has 16 divisors (see below), whose sum is σ = 39958272. Its totient is φ = 8324400.

The previous prime is 21505009. The next prime is 21505013. The reversal of 21505010 is 1050512.

It is not an unprimeable number, because it can be changed into a prime (21505013) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 34376 + ... + 34995.

It is an arithmetic number, because the mean of its divisors is an integer number (2497392).

Almost surely, 2^21505010 is an apocalyptic number.

21505010 is a deficient number, since it is larger than the sum of its proper divisors (18453262).

21505010 is a wasteful number, since it uses less digits than its factorization.

21505010 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69409.

The product of its (nonzero) digits is 50, while the sum is 14.

The square root of 21505010 is about 4637.3494584730. The cubic root of 21505010 is about 278.0864851772.

Adding to 21505010 its reverse (1050512), we get a palindrome (22555522).

The spelling of 21505010 in words is "twenty-one million, five hundred five thousand, ten".