21005315236 has 6 divisors (see below), whose sum is σ = 36759301670. Its totient is φ = 10502657616.

The previous prime is 21005315213. The next prime is 21005315249. The reversal of 21005315236 is 63251350012.

It can be written as a sum of positive squares in only one way, i.e., 16989558336 + 4015756900 = 130344^2 + 63370^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2625664401 + ... + 2625664408.

Almost surely, 2^21005315236 is an apocalyptic number.

It is an amenable number.

21005315236 is a deficient number, since it is larger than the sum of its proper divisors (15753986434).

21005315236 is a wasteful number, since it uses less digits than its factorization.

21005315236 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5251328813 (or 5251328811 counting only the distinct ones).

The product of its (nonzero) digits is 5400, while the sum is 28.

Adding to 21005315236 its reverse (63251350012), we get a palindrome (84256665248).

The spelling of 21005315236 in words is "twenty-one billion, five million, three hundred fifteen thousand, two hundred thirty-six".