21917012 has 24 divisors (see below), whose sum is σ = 43736616. Its totient is φ = 9520128.

The previous prime is 21917003. The next prime is 21917023. The reversal of 21917012 is 21071912.

It can be written as a sum of positive squares in 4 ways, for example, as 8271376 + 13645636 = 2876^2 + 3694^2 .

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11513 + ... + 13280.

It is an arithmetic number, because the mean of its divisors is an integer number (1822359).

Almost surely, 2^21917012 is an apocalyptic number.

It is an amenable number.

21917012 is a deficient number, since it is larger than the sum of its proper divisors (21819604).

21917012 is a wasteful number, since it uses less digits than its factorization.

21917012 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24827 (or 24825 counting only the distinct ones).

The product of its (nonzero) digits is 252, while the sum is 23.

The square root of 21917012 is about 4681.5608508274. The cubic root of 21917012 is about 279.8511623941.

Adding to 21917012 its reverse (21071912), we get a palindrome (42988924).

The spelling of 21917012 in words is "twenty-one million, nine hundred seventeen thousand, twelve".