21870971 has 2 divisors, whose sum is σ = 21870972. Its totient is φ = 21870970.

The previous prime is 21870967. The next prime is 21870973. The reversal of 21870971 is 17907812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21870971 - 2² = 21870967 is a prime.

Together with 21870973, 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 (21870973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10935485 + 10935486.

It is an arithmetic number, because the mean of its divisors is an integer number (10935486).

Almost surely, 2^21870971 is an apocalyptic number.

21870971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21870971 is an equidigital number, since it uses as much as digits as its factorization.

21870971 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7056, while the sum is 35.

The square root of 21870971 is about 4676.6409954154. The cubic root of 21870971 is about 279.6550641890.

The spelling of 21870971 in words is "twenty-one million, eight hundred seventy thousand, nine hundred seventy-one".