81220787 has 2 divisors, whose sum is σ = 81220788. Its totient is φ = 81220786.

The previous prime is 81220759. The next prime is 81220807. The reversal of 81220787 is 78702218.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81220787 - 2⁶ = 81220723 is a prime.

It is equal to p_4736645 and since 81220787 and 4736645 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (81220187) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40610393 + 40610394.

It is an arithmetic number, because the mean of its divisors is an integer number (40610394).

Almost surely, 2^81220787 is an apocalyptic number.

81220787 is a deficient number, since it is larger than the sum of its proper divisors (1).

81220787 is an equidigital number, since it uses as much as digits as its factorization.

81220787 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12544, while the sum is 35.

The square root of 81220787 is about 9012.2575972949. The cubic root of 81220787 is about 433.0676378471.

Subtracting from 81220787 its reverse (78702218), we obtain a square (2518569 = 1587²).

The spelling of 81220787 in words is "eighty-one million, two hundred twenty thousand, seven hundred eighty-seven".