21221081 has 16 divisors (see below), whose sum is σ = 26357760. Its totient is φ = 16673040.

The previous prime is 21221077. The next prime is 21221099. The reversal of 21221081 is 18012212.

It is a happy number.

It is not a de Polignac number, because 21221081 - 2² = 21221077 is a prime.

It is a super-2 number, since 2×21221081² = 900668557617122, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21221021) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1550 + ... + 6696.

It is an arithmetic number, because the mean of its divisors is an integer number (1647360).

Almost surely, 2^21221081 is an apocalyptic number.

It is an amenable number.

21221081 is a deficient number, since it is larger than the sum of its proper divisors (5136679).

21221081 is a wasteful number, since it uses less digits than its factorization.

21221081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5204.

The product of its (nonzero) digits is 64, while the sum is 17.

The square root of 21221081 is about 4606.6344547837. The cubic root of 21221081 is about 276.8572076577.

Adding to 21221081 its reverse (18012212), we get a palindrome (39233293).

The spelling of 21221081 in words is "twenty-one million, two hundred twenty-one thousand, eighty-one".