78221971 has 2 divisors, whose sum is σ = 78221972. Its totient is φ = 78221970.

The previous prime is 78221951. The next prime is 78221989. The reversal of 78221971 is 17912287.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 78221971 - 2¹⁵ = 78189203 is a prime.

It is a super-2 number, since 2×78221971² = 12237353494249682, which contains 22 as substring.

It is equal to p_4571785 and since 78221971 and 4571785 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 78221971.

It is not a weakly prime, because it can be changed into another prime (78221951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39110985 + 39110986.

It is an arithmetic number, because the mean of its divisors is an integer number (39110986).

Almost surely, 2^78221971 is an apocalyptic number.

78221971 is a deficient number, since it is larger than the sum of its proper divisors (1).

78221971 is an equidigital number, since it uses as much as digits as its factorization.

78221971 is an evil number, because the sum of its binary digits is even.

The product of its digits is 14112, while the sum is 37.

The square root of 78221971 is about 8844.3185718290. The cubic root of 78221971 is about 427.6707861558.

The spelling of 78221971 in words is "seventy-eight million, two hundred twenty-one thousand, nine hundred seventy-one".