21210957 has 8 divisors (see below), whose sum is σ = 31423680. Its totient is φ = 14140620.

The previous prime is 21210949. The next prime is 21210961. The reversal of 21210957 is 75901212.

It is not a de Polignac number, because 21210957 - 2³ = 21210949 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 785591 = 21210957 / (2 + 1 + 2 + 1 + 0 + 9 + 5 + 7).

It is a self number, because there is not a number n which added to its sum of digits gives 21210957.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210907) 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 7 ways as a sum of consecutive naturals, for example, 392769 + ... + 392822.

It is an arithmetic number, because the mean of its divisors is an integer number (3927960).

Almost surely, 2^21210957 is an apocalyptic number.

21210957 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21210957 is a deficient number, since it is larger than the sum of its proper divisors (10212723).

21210957 is an equidigital number, since it uses as much as digits as its factorization.

21210957 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 785600 (or 785594 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 27.

The square root of 21210957 is about 4605.5354737533. The cubic root of 21210957 is about 276.8131736424.

The spelling of 21210957 in words is "twenty-one million, two hundred ten thousand, nine hundred fifty-seven".