81630261 has 24 divisors (see below), whose sum is σ = 124304544. Its totient is φ = 53518320.

The previous prime is 81630257. The next prime is 81630287. The reversal of 81630261 is 16203618.

81630261 is a `hidden beast` number, since 8 + 1 + 630 + 26 + 1 = 666.

It is not a de Polignac number, because 81630261 - 2² = 81630257 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81630961) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 12070 + ... + 17576.

It is an arithmetic number, because the mean of its divisors is an integer number (5179356).

Almost surely, 2^81630261 is an apocalyptic number.

81630261 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

It is an amenable number.

81630261 is a deficient number, since it is larger than the sum of its proper divisors (42674283).

81630261 is an equidigital number, since it uses as much as digits as its factorization.

81630261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5583 (or 5571 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 81630261 is about 9034.9466517517. The cubic root of 81630261 is about 433.7941873500.

Adding to 81630261 its reverse (16203618), we get a palindrome (97833879).

The spelling of 81630261 in words is "eighty-one million, six hundred thirty thousand, two hundred sixty-one".