21512005 has 8 divisors (see below), whose sum is σ = 26168472. Its totient is φ = 16973568.

The previous prime is 21511999. The next prime is 21512017. The reversal of 21512005 is 50021512.

It can be written as a sum of positive squares in 4 ways, for example, as 961 + 21511044 = 31^2 + 4638^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21512005 - 2⁹ = 21511493 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21512005.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 29104 + ... + 29833.

It is an arithmetic number, because the mean of its divisors is an integer number (3271059).

Almost surely, 2^21512005 is an apocalyptic number.

It is an amenable number.

21512005 is a deficient number, since it is larger than the sum of its proper divisors (4656467).

21512005 is an equidigital number, since it uses as much as digits as its factorization.

21512005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59015.

The product of its (nonzero) digits is 100, while the sum is 16.

The square root of 21512005 is about 4638.1035995329. The cubic root of 21512005 is about 278.1166332542.

Adding to 21512005 its reverse (50021512), we get a palindrome (71533517).

The spelling of 21512005 in words is "twenty-one million, five hundred twelve thousand, five".