21501099 has 8 divisors (see below), whose sum is σ = 31853520. Its totient is φ = 14334048.

The previous prime is 21501091. The next prime is 21501101. The reversal of 21501099 is 99010512.

It is a happy number.

It is not a de Polignac number, because 21501099 - 2³ = 21501091 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: 796337 = 21501099 / (2 + 1 + 5 + 0 + 1 + 0 + 9 + 9).

It is not an unprimeable number, because it can be changed into a prime (21501091) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 398142 + ... + 398195.

It is an arithmetic number, because the mean of its divisors is an integer number (3981690).

Almost surely, 2^21501099 is an apocalyptic number.

21501099 is a deficient number, since it is larger than the sum of its proper divisors (10352421).

21501099 is an equidigital number, since it uses as much as digits as its factorization.

21501099 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 796346 (or 796340 counting only the distinct ones).

The product of its (nonzero) digits is 810, while the sum is 27.

The square root of 21501099 is about 4636.9277544512. The cubic root of 21501099 is about 278.0696261261.

It can be divided in two parts, 2150 and 1099, that added together give a square (3249 = 57²).

The spelling of 21501099 in words is "twenty-one million, five hundred one thousand, ninety-nine".