21451989 has 16 divisors (see below), whose sum is σ = 30889152. Its totient is φ = 13164288.

The previous prime is 21451981. The next prime is 21452021. The reversal of 21451989 is 98915412.

It is not a de Polignac number, because 21451989 - 2³ = 21451981 is a prime.

It is a super-2 number, since 2×21451989² = 920375664112242, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21451981) 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 15 ways as a sum of consecutive naturals, for example, 21469 + ... + 22445.

It is an arithmetic number, because the mean of its divisors is an integer number (1930572).

Almost surely, 2^21451989 is an apocalyptic number.

It is an amenable number.

21451989 is a deficient number, since it is larger than the sum of its proper divisors (9437163).

21451989 is a wasteful number, since it uses less digits than its factorization.

21451989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1556.

The product of its digits is 25920, while the sum is 39.

The square root of 21451989 is about 4631.6291950026. The cubic root of 21451989 is about 277.8577546363.

The spelling of 21451989 in words is "twenty-one million, four hundred fifty-one thousand, nine hundred eighty-nine".