21932991 has 16 divisors (see below), whose sum is σ = 33287520. Its totient is φ = 14264640.

The previous prime is 21932983. The next prime is 21932993. The reversal of 21932991 is 19923912.

It is a happy number.

It is not a de Polignac number, because 21932991 - 2³ = 21932983 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21932993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8800 + ... + 11013.

It is an arithmetic number, because the mean of its divisors is an integer number (2080470).

Almost surely, 2^21932991 is an apocalyptic number.

21932991 is a deficient number, since it is larger than the sum of its proper divisors (11354529).

21932991 is a wasteful number, since it uses less digits than its factorization.

21932991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19863 (or 19857 counting only the distinct ones).

The product of its digits is 8748, while the sum is 36.

The square root of 21932991 is about 4683.2671288322. The cubic root of 21932991 is about 279.9191560821.

It can be divided in two parts, 2193 and 2991, that added together give a square (5184 = 72²).

The spelling of 21932991 in words is "twenty-one million, nine hundred thirty-two thousand, nine hundred ninety-one".