21581226 has 24 divisors (see below), whose sum is σ = 49221120. Its totient is φ = 6815016.

The previous prime is 21581221. The next prime is 21581233. The reversal of 21581226 is 62218512.

It is a happy number.

It is a super-4 number, since 4×21581226⁴ (a number of 30 digits) contains 4444 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21581226.

It is not an unprimeable number, because it can be changed into a prime (21581221) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 31210 + ... + 31893.

It is an arithmetic number, because the mean of its divisors is an integer number (2050880).

Almost surely, 2^21581226 is an apocalyptic number.

21581226 is an abundant number, since it is smaller than the sum of its proper divisors (27639894).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21581226 is a wasteful number, since it uses less digits than its factorization.

21581226 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63130 (or 63127 counting only the distinct ones).

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

The square root of 21581226 is about 4645.5598155658. The cubic root of 21581226 is about 278.4146203430.

Adding to 21581226 its reverse (62218512), we get a palindrome (83799738).

The spelling of 21581226 in words is "twenty-one million, five hundred eighty-one thousand, two hundred twenty-six".