21901989 has 16 divisors (see below), whose sum is σ = 30712320. Its totient is φ = 13863360.

The previous prime is 21901981. The next prime is 21901993. The reversal of 21901989 is 98910912.

It is a happy number.

It is not a de Polignac number, because 21901989 - 2³ = 21901981 is a prime.

It is a super-2 number, since 2×21901989² = 959394244312242, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21901981) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3244 + ... + 7370.

It is an arithmetic number, because the mean of its divisors is an integer number (1919520).

Almost surely, 2^21901989 is an apocalyptic number.

21901989 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21901989 is a deficient number, since it is larger than the sum of its proper divisors (8810331).

21901989 is a wasteful number, since it uses less digits than its factorization.

21901989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4220.

The product of its (nonzero) digits is 11664, while the sum is 39.

The square root of 21901989 is about 4679.9560895376. The cubic root of 21901989 is about 279.7872065202.

The spelling of 21901989 in words is "twenty-one million, nine hundred one thousand, nine hundred eighty-nine".