21390957 has 12 divisors (see below), whose sum is σ = 35312160. Its totient is φ = 12223368.

The previous prime is 21390911. The next prime is 21390977. The reversal of 21390957 is 75909312.

It is not a de Polignac number, because 21390957 - 2¹⁰ = 21389933 is a prime.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21390977) 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 11 ways as a sum of consecutive naturals, for example, 169707 + ... + 169832.

It is an arithmetic number, because the mean of its divisors is an integer number (2942680).

Almost surely, 2^21390957 is an apocalyptic number.

It is an amenable number.

21390957 is a deficient number, since it is larger than the sum of its proper divisors (13921203).

21390957 is a wasteful number, since it uses less digits than its factorization.

21390957 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 339552 (or 339549 counting only the distinct ones).

The product of its (nonzero) digits is 17010, while the sum is 36.

The square root of 21390957 is about 4625.0358917526. The cubic root of 21390957 is about 277.5939978618.

The spelling of 21390957 in words is "twenty-one million, three hundred ninety thousand, nine hundred fifty-seven".