71221991 has 2 divisors, whose sum is σ = 71221992. Its totient is φ = 71221990.

The previous prime is 71221957. The next prime is 71222023. The reversal of 71221991 is 19912217.

It is an a-pointer prime, because the next prime (71222023) can be obtained adding 71221991 to its sum of digits (32).

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 71221991 - 2²⁶ = 4113127 is a prime.

It is equal to p_4185644 and since 71221991 and 4185644 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (71221921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 35610995 + 35610996.

It is an arithmetic number, because the mean of its divisors is an integer number (35610996).

Almost surely, 2^71221991 is an apocalyptic number.

71221991 is a deficient number, since it is larger than the sum of its proper divisors (1).

71221991 is an equidigital number, since it uses as much as digits as its factorization.

71221991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2268, while the sum is 32.

The square root of 71221991 is about 8439.3122350106. The cubic root of 71221991 is about 414.5128866361.

The spelling of 71221991 in words is "seventy-one million, two hundred twenty-one thousand, nine hundred ninety-one".