81669451 has 2 divisors, whose sum is σ = 81669452. Its totient is φ = 81669450.

The previous prime is 81669443. The next prime is 81669463. The reversal of 81669451 is 15496618.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81669451 - 2³ = 81669443 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81669431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40834725 + 40834726.

It is an arithmetic number, because the mean of its divisors is an integer number (40834726).

Almost surely, 2^81669451 is an apocalyptic number.

81669451 is a deficient number, since it is larger than the sum of its proper divisors (1).

81669451 is an equidigital number, since it uses as much as digits as its factorization.

81669451 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 51840, while the sum is 40.

The square root of 81669451 is about 9037.1151923609. The cubic root of 81669451 is about 433.8635965541.

The spelling of 81669451 in words is "eighty-one million, six hundred sixty-nine thousand, four hundred fifty-one".