21503971 has 2 divisors, whose sum is σ = 21503972. Its totient is φ = 21503970.

The previous prime is 21503969. The next prime is 21503981. The reversal of 21503971 is 17930512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21503971 - 2¹ = 21503969 is a prime.

Together with 21503969, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21503981) by changing a digit.

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 as a sum of consecutive naturals, namely, 10751985 + 10751986.

It is an arithmetic number, because the mean of its divisors is an integer number (10751986).

Almost surely, 2^21503971 is an apocalyptic number.

21503971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21503971 is an equidigital number, since it uses as much as digits as its factorization.

21503971 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1890, while the sum is 28.

The square root of 21503971 is about 4637.2374319200. The cubic root of 21503971 is about 278.0820065849.

The spelling of 21503971 in words is "twenty-one million, five hundred three thousand, nine hundred seventy-one".