21225881 has 2 divisors, whose sum is σ = 21225882. Its totient is φ = 21225880.

The previous prime is 21225863. The next prime is 21225943. The reversal of 21225881 is 18852212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11560000 + 9665881 = 3400^2 + 3109^2 .

It is a cyclic number.

It is not a de Polignac number, because 21225881 - 2⁶ = 21225817 is a prime.

It is a super-2 number, since 2×21225881² = 901076048452322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21225851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10612940 + 10612941.

It is an arithmetic number, because the mean of its divisors is an integer number (10612941).

Almost surely, 2^21225881 is an apocalyptic number.

It is an amenable number.

21225881 is a deficient number, since it is larger than the sum of its proper divisors (1).

21225881 is an equidigital number, since it uses as much as digits as its factorization.

21225881 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2560, while the sum is 29.

The square root of 21225881 is about 4607.1554130504. The cubic root of 21225881 is about 276.8780802107.

The spelling of 21225881 in words is "twenty-one million, two hundred twenty-five thousand, eight hundred eighty-one".