21951971 has 2 divisors, whose sum is σ = 21951972. Its totient is φ = 21951970.

The previous prime is 21951931. The next prime is 21951977. The reversal of 21951971 is 17915912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21951971 - 2¹⁸ = 21689827 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (21951977) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10975985 + 10975986.

It is an arithmetic number, because the mean of its divisors is an integer number (10975986).

Almost surely, 2^21951971 is an apocalyptic number.

21951971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21951971 is an equidigital number, since it uses as much as digits as its factorization.

21951971 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5670, while the sum is 35.

The square root of 21951971 is about 4685.2930538014. The cubic root of 21951971 is about 279.9998767006. Note that the first 3 decimals are identical.

It can be divided in two parts, 21951 and 971, that added together give a palindrome (22922).

The spelling of 21951971 in words is "twenty-one million, nine hundred fifty-one thousand, nine hundred seventy-one".