21015650 has 12 divisors (see below), whose sum is σ = 39089202. Its totient is φ = 8406240.

The previous prime is 21015649. The next prime is 21015671. The reversal of 21015650 is 5651012.

It can be written as a sum of positive squares in 3 ways, for example, as 12117361 + 8898289 = 3481^2 + 2983^2 .

It is a hoax number, since the sum of its digits (20) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 210107 + ... + 210206.

Almost surely, 2^21015650 is an apocalyptic number.

21015650 is a deficient number, since it is larger than the sum of its proper divisors (18073552).

21015650 is a wasteful number, since it uses less digits than its factorization.

21015650 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 420325 (or 420320 counting only the distinct ones).

The product of its (nonzero) digits is 300, while the sum is 20.

The square root of 21015650 is about 4584.2829319317. The cubic root of 21015650 is about 275.9609358001.

Adding to 21015650 its reverse (5651012), we get a palindrome (26666662).

The spelling of 21015650 in words is "twenty-one million, fifteen thousand, six hundred fifty".