21988417 has 4 divisors (see below), whose sum is σ = 23987376. Its totient is φ = 19989460.

The previous prime is 21988411. The next prime is 21988451. The reversal of 21988417 is 71488912.

It is a happy number.

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 21988417 - 2¹¹ = 21986369 is a prime.

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 21988417.

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, 999463 + ... + 999484.

It is an arithmetic number, because the mean of its divisors is an integer number (5996844).

Almost surely, 2^21988417 is an apocalyptic number.

It is an amenable number.

21988417 is a deficient number, since it is larger than the sum of its proper divisors (1998959).

21988417 is a wasteful number, since it uses less digits than its factorization.

21988417 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1998958.

The product of its digits is 32256, while the sum is 40.

The square root of 21988417 is about 4689.1808453076. The cubic root of 21988417 is about 280.1547486424.

The spelling of 21988417 in words is "twenty-one million, nine hundred eighty-eight thousand, four hundred seventeen".