21515147 has 8 divisors (see below), whose sum is σ = 22272000. Its totient is φ = 20762280.

The previous prime is 21515113. The next prime is 21515159. The reversal of 21515147 is 74151512.

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 21515147 - 2⁶ = 21515083 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21515647) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13604 + ... + 15102.

It is an arithmetic number, because the mean of its divisors is an integer number (2784000).

Almost surely, 2^21515147 is an apocalyptic number.

21515147 is a deficient number, since it is larger than the sum of its proper divisors (756853).

21515147 is a wasteful number, since it uses less digits than its factorization.

21515147 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1993.

The product of its digits is 1400, while the sum is 26.

The square root of 21515147 is about 4638.4423031876. The cubic root of 21515147 is about 278.1301729796.

Adding to 21515147 its reverse (74151512), we get a palindrome (95666659).

The spelling of 21515147 in words is "twenty-one million, five hundred fifteen thousand, one hundred forty-seven".