21999631 has 4 divisors (see below), whose sum is σ = 22194432. Its totient is φ = 21804832.

The previous prime is 21999629. The next prime is 21999641. The reversal of 21999631 is 13699912.

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

It is a cyclic number.

It is not a de Polignac number, because 21999631 - 2¹ = 21999629 is a prime.

It is a super-2 number, since 2×21999631² = 967967528272322, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21999641) 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, 97231 + ... + 97456.

It is an arithmetic number, because the mean of its divisors is an integer number (5548608).

Almost surely, 2^21999631 is an apocalyptic number.

21999631 is a deficient number, since it is larger than the sum of its proper divisors (194801).

21999631 is a wasteful number, since it uses less digits than its factorization.

21999631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 194800.

The product of its digits is 26244, while the sum is 40.

The square root of 21999631 is about 4690.3764241263. The cubic root of 21999631 is about 280.2023664621.

The spelling of 21999631 in words is "twenty-one million, nine hundred ninety-nine thousand, six hundred thirty-one".