21430973 has 4 divisors (see below), whose sum is σ = 21514620. Its totient is φ = 21347328.

The previous prime is 21430957. The next prime is 21430979. The reversal of 21430973 is 37903412.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 17322244 + 4108729 = 4162^2 + 2027^2 .

It is a cyclic number.

It is not a de Polignac number, because 21430973 - 2⁴ = 21430957 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21430979) 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, 41438 + ... + 41951.

It is an arithmetic number, because the mean of its divisors is an integer number (5378655).

Almost surely, 2^21430973 is an apocalyptic number.

It is an amenable number.

21430973 is a deficient number, since it is larger than the sum of its proper divisors (83647).

21430973 is an equidigital number, since it uses as much as digits as its factorization.

21430973 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83646.

The product of its (nonzero) digits is 4536, while the sum is 29.

The square root of 21430973 is about 4629.3598909568. The cubic root of 21430973 is about 277.7669881261.

The spelling of 21430973 in words is "twenty-one million, four hundred thirty thousand, nine hundred seventy-three".