21515245 has 8 divisors (see below), whose sum is σ = 26708760. Its totient is φ = 16618560.

The previous prime is 21515233. The next prime is 21515257. The reversal of 21515245 is 54251512.

It is an interprime number because it is at equal distance from previous prime (21515233) and next prime (21515257).

It can be written as a sum of positive squares in 4 ways, for example, as 161604 + 21353641 = 402^2 + 4621^2 .

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

It is not a de Polignac number, because 21515245 - 2¹¹ = 21513197 is a prime.

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, 74046 + ... + 74335.

It is an arithmetic number, because the mean of its divisors is an integer number (3338595).

Almost surely, 2^21515245 is an apocalyptic number.

It is an amenable number.

21515245 is a deficient number, since it is larger than the sum of its proper divisors (5193515).

21515245 is a wasteful number, since it uses less digits than its factorization.

21515245 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 148415.

The product of its digits is 2000, while the sum is 25.

The square root of 21515245 is about 4638.4528670668. The cubic root of 21515245 is about 278.1305952668.

Adding to 21515245 its reverse (54251512), we get a palindrome (75766757).

It can be divided in two parts, 2151 and 5245, that added together give a square (7396 = 86²).

The spelling of 21515245 in words is "twenty-one million, five hundred fifteen thousand, two hundred forty-five".