21971707 has 2 divisors, whose sum is σ = 21971708. Its totient is φ = 21971706.

The previous prime is 21971687. The next prime is 21971711. The reversal of 21971707 is 70717912.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21971707 is a prime.

It is not a weakly prime, because it can be changed into another prime (21971737) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10985853 + 10985854.

It is an arithmetic number, because the mean of its divisors is an integer number (10985854).

Almost surely, 2^21971707 is an apocalyptic number.

21971707 is a deficient number, since it is larger than the sum of its proper divisors (1).

21971707 is an equidigital number, since it uses as much as digits as its factorization.

21971707 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6174, while the sum is 34.

The square root of 21971707 is about 4687.3987455731. The cubic root of 21971707 is about 280.0837632047.

The spelling of 21971707 in words is "twenty-one million, nine hundred seventy-one thousand, seven hundred seven".