21115428 has 48 divisors (see below), whose sum is σ = 52799040. Its totient is φ = 6544384.

The previous prime is 21115427. The next prime is 21115429. The reversal of 21115428 is 82451112.

It is an interprime number because it is at equal distance from previous prime (21115427) and next prime (21115429).

It is a super-2 number, since 2×21115428² = 891722599246368, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21115398 and 21115407.

It is not an unprimeable number, because it can be changed into a prime (21115421) 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, 17575 + ... + 18737.

It is an arithmetic number, because the mean of its divisors is an integer number (1099980).

Almost surely, 2^21115428 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21115428, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26399520).

21115428 is an abundant number, since it is smaller than the sum of its proper divisors (31683612).

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

21115428 is a wasteful number, since it uses less digits than its factorization.

21115428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1276 (or 1274 counting only the distinct ones).

The product of its digits is 640, while the sum is 24.

The square root of 21115428 is about 4595.1526634052. The cubic root of 21115428 is about 276.3969817667.

The spelling of 21115428 in words is "twenty-one million, one hundred fifteen thousand, four hundred twenty-eight".