21321957 has 8 divisors (see below), whose sum is σ = 28454400. Its totient is φ = 14202080.

The previous prime is 21321947. The next prime is 21321959. The reversal of 21321957 is 75912312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21321957 - 2⁴ = 21321941 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21321959) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2044 + ... + 6842.

It is an arithmetic number, because the mean of its divisors is an integer number (3556800).

Almost surely, 2^21321957 is an apocalyptic number.

It is an amenable number.

21321957 is a deficient number, since it is larger than the sum of its proper divisors (7132443).

21321957 is a wasteful number, since it uses less digits than its factorization.

21321957 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6283.

The product of its digits is 3780, while the sum is 30.

The square root of 21321957 is about 4617.5704650823. The cubic root of 21321957 is about 277.2952015433.

The spelling of 21321957 in words is "twenty-one million, three hundred twenty-one thousand, nine hundred fifty-seven".