21257099 has 4 divisors (see below), whose sum is σ = 21289920. Its totient is φ = 21224280.

The previous prime is 21257077. The next prime is 21257101. The reversal of 21257099 is 99075212.

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

It is a cyclic number.

It is not a de Polignac number, because 21257099 - 2⁸ = 21256843 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21257059) 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, 15419 + ... + 16740.

It is an arithmetic number, because the mean of its divisors is an integer number (5322480).

Almost surely, 2^21257099 is an apocalyptic number.

21257099 is a deficient number, since it is larger than the sum of its proper divisors (32821).

21257099 is an equidigital number, since it uses as much as digits as its factorization.

21257099 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32820.

The product of its (nonzero) digits is 11340, while the sum is 35.

The square root of 21257099 is about 4610.5421590091. The cubic root of 21257099 is about 277.0137533519.

The spelling of 21257099 in words is "twenty-one million, two hundred fifty-seven thousand, ninety-nine".