21515201 has 16 divisors (see below), whose sum is σ = 23587200. Its totient is φ = 19555200.

The previous prime is 21515171. The next prime is 21515203. The reversal of 21515201 is 10251512.

It is a cyclic number.

It is not a de Polignac number, because 21515201 - 2¹⁴ = 21498817 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 21515201.

It is not an unprimeable number, because it can be changed into a prime (21515203) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 55115 + ... + 55503.

It is an arithmetic number, because the mean of its divisors is an integer number (1474200).

Almost surely, 2^21515201 is an apocalyptic number.

It is an amenable number.

21515201 is a deficient number, since it is larger than the sum of its proper divisors (2071999).

21515201 is a wasteful number, since it uses less digits than its factorization.

21515201 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 520.

The product of its (nonzero) digits is 100, while the sum is 17.

The square root of 21515201 is about 4638.4481241036. The cubic root of 21515201 is about 278.1304056686.

Adding to 21515201 its reverse (10251512), we get a palindrome (31766713).

The spelling of 21515201 in words is "twenty-one million, five hundred fifteen thousand, two hundred one".