21257106 has 96 divisors (see below), whose sum is σ = 51988608. Its totient is φ = 5744640.

The previous prime is 21257101. The next prime is 21257107. The reversal of 21257106 is 60175212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21257101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 518446 + ... + 518486.

It is an arithmetic number, because the mean of its divisors is an integer number (541548).

Almost surely, 2^21257106 is an apocalyptic number.

21257106 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 21257106, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25994304).

21257106 is an abundant number, since it is smaller than the sum of its proper divisors (30731502).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21257106 is a wasteful number, since it uses less digits than its factorization.

21257106 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 116 (or 99 counting only the distinct ones).

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 21257106 is about 4610.5429181388. The cubic root of 21257106 is about 277.0137837589.

The spelling of 21257106 in words is "twenty-one million, two hundred fifty-seven thousand, one hundred six".