81562221 has 24 divisors (see below), whose sum is σ = 131578720. Its totient is φ = 50190192.

The previous prime is 81562219. The next prime is 81562241. The reversal of 81562221 is 12226518.

It is a happy number.

81562221 is a `hidden beast` number, since 8 + 15 + 622 + 21 = 666.

It is not a de Polignac number, because 81562221 - 2¹ = 81562219 is a prime.

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 (81562241) 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, 9751 + ... + 16068.

Almost surely, 2^81562221 is an apocalyptic number.

81562221 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

It is an amenable number.

81562221 is a deficient number, since it is larger than the sum of its proper divisors (50016499).

81562221 is a wasteful number, since it uses less digits than its factorization.

81562221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25847 (or 25835 counting only the distinct ones).

The product of its digits is 1920, while the sum is 27.

The square root of 81562221 is about 9031.1804876218. The cubic root of 81562221 is about 433.6736292774.

Adding to 81562221 its reverse (12226518), we get a palindrome (93788739).

It can be divided in two parts, 815 and 62221, that added together give a palindrome (63036).

The spelling of 81562221 in words is "eighty-one million, five hundred sixty-two thousand, two hundred twenty-one".