21124999 has 16 divisors (see below), whose sum is σ = 25740288. Its totient is φ = 16924032.

The previous prime is 21124993. The next prime is 21125003. The reversal of 21124999 is 99942112.

It is a cyclic number.

It is not a de Polignac number, because 21124999 - 2⁵ = 21124967 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21124993) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19342 + ... + 20404.

It is an arithmetic number, because the mean of its divisors is an integer number (1608768).

Almost surely, 2^21124999 is an apocalyptic number.

21124999 is a deficient number, since it is larger than the sum of its proper divisors (4615289).

21124999 is a wasteful number, since it uses less digits than its factorization.

21124999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1254.

The product of its digits is 11664, while the sum is 37.

The square root of 21124999 is about 4596.1939689269. The cubic root of 21124999 is about 276.4387363220.

The spelling of 21124999 in words is "twenty-one million, one hundred twenty-four thousand, nine hundred ninety-nine".