21881667 has 4 divisors (see below), whose sum is σ = 29175560. Its totient is φ = 14587776.

The previous prime is 21881663. The next prime is 21881681. The reversal of 21881667 is 76618812.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21881667 - 2² = 21881663 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21881663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3646942 + ... + 3646947.

It is an arithmetic number, because the mean of its divisors is an integer number (7293890).

Almost surely, 2^21881667 is an apocalyptic number.

21881667 is a deficient number, since it is larger than the sum of its proper divisors (7293893).

21881667 is an equidigital number, since it uses as much as digits as its factorization.

21881667 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7293892.

The product of its digits is 32256, while the sum is 39.

The square root of 21881667 is about 4677.7844114495. The cubic root of 21881667 is about 279.7006452026.

The spelling of 21881667 in words is "twenty-one million, eight hundred eighty-one thousand, six hundred sixty-seven".