81791401 has 2 divisors, whose sum is σ = 81791402. Its totient is φ = 81791400.

The previous prime is 81791399. The next prime is 81791417. The reversal of 81791401 is 10419718.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 51552400 + 30239001 = 7180^2 + 5499^2 .

It is a cyclic number.

It is not a de Polignac number, because 81791401 - 2¹ = 81791399 is a prime.

Together with 81791399, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (81791441) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40895700 + 40895701.

It is an arithmetic number, because the mean of its divisors is an integer number (40895701).

Almost surely, 2^81791401 is an apocalyptic number.

It is an amenable number.

81791401 is a deficient number, since it is larger than the sum of its proper divisors (1).

81791401 is an equidigital number, since it uses as much as digits as its factorization.

81791401 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2016, while the sum is 31.

The square root of 81791401 is about 9043.8598507496. The cubic root of 81791401 is about 434.0794396126.

The spelling of 81791401 in words is "eighty-one million, seven hundred ninety-one thousand, four hundred one".