81962509 has 2 divisors, whose sum is σ = 81962510. Its totient is φ = 81962508.

The previous prime is 81962479. The next prime is 81962519. The reversal of 81962509 is 90526918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 53978409 + 27984100 = 7347^2 + 5290^2 .

It is a cyclic number.

It is not a de Polignac number, because 81962509 - 2²³ = 73573901 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81962519) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40981254 + 40981255.

It is an arithmetic number, because the mean of its divisors is an integer number (40981255).

Almost surely, 2^81962509 is an apocalyptic number.

It is an amenable number.

81962509 is a deficient number, since it is larger than the sum of its proper divisors (1).

81962509 is an equidigital number, since it uses as much as digits as its factorization.

81962509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 38880, while the sum is 40.

The square root of 81962509 is about 9053.3148072957. The cubic root of 81962509 is about 434.3819275261.

The spelling of 81962509 in words is "eighty-one million, nine hundred sixty-two thousand, five hundred nine".