21428500 has 48 divisors (see below), whose sum is σ = 49572432. Its totient is φ = 8064000.

The previous prime is 21428497. The next prime is 21428503. The reversal of 21428500 is 582412.

It is an interprime number because it is at equal distance from previous prime (21428497) and next prime (21428503).

It can be written as a sum of positive squares in 8 ways, for example, as 11806096 + 9622404 = 3436^2 + 3102^2 .

It is a super-2 number, since 2×21428500² = 918361224500000, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21428503) 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, 7240 + ... + 9760.

It is an arithmetic number, because the mean of its divisors is an integer number (1032759).

Almost surely, 2^21428500 is an apocalyptic number.

21428500 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21428500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24786216).

21428500 is an abundant number, since it is smaller than the sum of its proper divisors (28143932).

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

21428500 is a wasteful number, since it uses less digits than its factorization.

21428500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2557 (or 2545 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 22.

The square root of 21428500 is about 4629.0927836888. The cubic root of 21428500 is about 277.7563035251.

The spelling of 21428500 in words is "twenty-one million, four hundred twenty-eight thousand, five hundred".