21981699 has 20 divisors (see below), whose sum is σ = 33642840. Its totient is φ = 14294880.

The previous prime is 21981683. The next prime is 21981733. The reversal of 21981699 is 99618912.

It is not a de Polignac number, because 21981699 - 2⁴ = 21981683 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21981649) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 12 + ... + 6630.

It is an arithmetic number, because the mean of its divisors is an integer number (1682142).

Almost surely, 2^21981699 is an apocalyptic number.

21981699 is a deficient number, since it is larger than the sum of its proper divisors (11661141).

21981699 is an equidigital number, since it uses as much as digits as its factorization.

21981699 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6672 (or 6663 counting only the distinct ones).

The product of its digits is 69984, while the sum is 45.

The square root of 21981699 is about 4688.4644607803. The cubic root of 21981699 is about 280.1262143569.

It can be divided in two parts, 219 and 81699, that added together give a palindrome (81918).

The spelling of 21981699 in words is "twenty-one million, nine hundred eighty-one thousand, six hundred ninety-nine".