21771989 has 4 divisors (see below), whose sum is σ = 21796800. Its totient is φ = 21747180.

The previous prime is 21771983. The next prime is 21772001. The reversal of 21771989 is 98917712.

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 21771989 - 2⁸ = 21771733 is a prime.

It is a super-2 number, since 2×21771989² = 948039010032242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21771983) 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, 11039 + ... + 12860.

It is an arithmetic number, because the mean of its divisors is an integer number (5449200).

Almost surely, 2^21771989 is an apocalyptic number.

It is an amenable number.

21771989 is a deficient number, since it is larger than the sum of its proper divisors (24811).

21771989 is an equidigital number, since it uses as much as digits as its factorization.

21771989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24810.

The product of its digits is 63504, while the sum is 44.

The square root of 21771989 is about 4666.0463992549. The cubic root of 21771989 is about 279.2325455079.

The spelling of 21771989 in words is "twenty-one million, seven hundred seventy-one thousand, nine hundred eighty-nine".