21512147 has 2 divisors, whose sum is σ = 21512148. Its totient is φ = 21512146.

The previous prime is 21512143. The next prime is 21512213. The reversal of 21512147 is 74121512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21512147 - 2² = 21512143 is a prime.

It is not a weakly prime, because it can be changed into another prime (21512143) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10756073 + 10756074.

It is an arithmetic number, because the mean of its divisors is an integer number (10756074).

Almost surely, 2^21512147 is an apocalyptic number.

21512147 is a deficient number, since it is larger than the sum of its proper divisors (1).

21512147 is an equidigital number, since it uses as much as digits as its factorization.

21512147 is an evil number, because the sum of its binary digits is even.

The product of its digits is 560, while the sum is 23.

The square root of 21512147 is about 4638.1189074883. The cubic root of 21512147 is about 278.1172451989.

Adding to 21512147 its reverse (74121512), we get a palindrome (95633659).

The spelling of 21512147 in words is "twenty-one million, five hundred twelve thousand, one hundred forty-seven".