21029971 has 2 divisors, whose sum is σ = 21029972. Its totient is φ = 21029970.

The previous prime is 21029951. The next prime is 21029977. The reversal of 21029971 is 17992012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21029971 - 2¹³ = 21021779 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21029977) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10514985 + 10514986.

It is an arithmetic number, because the mean of its divisors is an integer number (10514986).

Almost surely, 2^21029971 is an apocalyptic number.

21029971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21029971 is an equidigital number, since it uses as much as digits as its factorization.

21029971 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2268, while the sum is 31.

The square root of 21029971 is about 4585.8446332164. The cubic root of 21029971 is about 276.0236055915.

The spelling of 21029971 in words is "twenty-one million, twenty-nine thousand, nine hundred seventy-one".