21872881 has 2 divisors, whose sum is σ = 21872882. Its totient is φ = 21872880.

The previous prime is 21872867. The next prime is 21872891. The reversal of 21872881 is 18827812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19439281 + 2433600 = 4409^2 + 1560^2 .

It is a cyclic number.

It is not a de Polignac number, because 21872881 - 2⁹ = 21872369 is a prime.

It is a super-2 number, since 2×21872881² = 956845846480322, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21872881.

It is not a weakly prime, because it can be changed into another prime (21872801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10936440 + 10936441.

It is an arithmetic number, because the mean of its divisors is an integer number (10936441).

Almost surely, 2^21872881 is an apocalyptic number.

It is an amenable number.

21872881 is a deficient number, since it is larger than the sum of its proper divisors (1).

21872881 is an equidigital number, since it uses as much as digits as its factorization.

21872881 is an evil number, because the sum of its binary digits is even.

The product of its digits is 14336, while the sum is 37.

The square root of 21872881 is about 4676.8451973526. The cubic root of 21872881 is about 279.6632047454.

The spelling of 21872881 in words is "twenty-one million, eight hundred seventy-two thousand, eight hundred eighty-one".