21988441 has 4 divisors (see below), whose sum is σ = 22004752. Its totient is φ = 21972132.

The previous prime is 21988411. The next prime is 21988451. The reversal of 21988441 is 14488912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21988441 - 2⁷ = 21988313 is a prime.

It is a super-2 number, since 2×21988441² = 966983075220962, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21988441.

It is not an unprimeable number, because it can be changed into a prime (21988411) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5931 + ... + 8896.

It is an arithmetic number, because the mean of its divisors is an integer number (5501188).

Almost surely, 2^21988441 is an apocalyptic number.

21988441 is the 2966-th heptagonal number.

It is an amenable number.

21988441 is a deficient number, since it is larger than the sum of its proper divisors (16311).

21988441 is a wasteful number, since it uses less digits than its factorization.

21988441 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16310.

The product of its digits is 18432, while the sum is 37.

The square root of 21988441 is about 4689.1834043893. The cubic root of 21988441 is about 280.1548505705.

The spelling of 21988441 in words is "twenty-one million, nine hundred eighty-eight thousand, four hundred forty-one".