81651979 has 2 divisors, whose sum is σ = 81651980. Its totient is φ = 81651978.

The previous prime is 81651971. The next prime is 81652049. The reversal of 81651979 is 97915618.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81651979 - 2³ = 81651971 is a prime.

It is not a weakly prime, because it can be changed into another prime (81651971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40825989 + 40825990.

It is an arithmetic number, because the mean of its divisors is an integer number (40825990).

Almost surely, 2^81651979 is an apocalyptic number.

81651979 is a deficient number, since it is larger than the sum of its proper divisors (1).

81651979 is an equidigital number, since it uses as much as digits as its factorization.

81651979 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 136080, while the sum is 46.

The square root of 81651979 is about 9036.1484604891. The cubic root of 81651979 is about 433.8326547299.

The spelling of 81651979 in words is "eighty-one million, six hundred fifty-one thousand, nine hundred seventy-nine".