21420689 has 4 divisors (see below), whose sum is σ = 21479424. Its totient is φ = 21361956.

The previous prime is 21420683. The next prime is 21420703. The reversal of 21420689 is 98602412.

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 21420689 - 2⁸ = 21420433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21420683) 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, 28817 + ... + 29550.

It is an arithmetic number, because the mean of its divisors is an integer number (5369856).

Almost surely, 2^21420689 is an apocalyptic number.

It is an amenable number.

21420689 is a deficient number, since it is larger than the sum of its proper divisors (58735).

21420689 is an equidigital number, since it uses as much as digits as its factorization.

21420689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58734.

The product of its (nonzero) digits is 6912, while the sum is 32.

The square root of 21420689 is about 4628.2490209581. The cubic root of 21420689 is about 277.7225506858.

The spelling of 21420689 in words is "twenty-one million, four hundred twenty thousand, six hundred eighty-nine".