21211428 has 48 divisors (see below), whose sum is σ = 59028480. Its totient is φ = 5796384.

The previous prime is 21211403. The next prime is 21211433. The reversal of 21211428 is 82411212.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3558 + ... + 7421.

It is an arithmetic number, because the mean of its divisors is an integer number (1229760).

Almost surely, 2^21211428 is an apocalyptic number.

21211428 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21211428 is an abundant number, since it is smaller than the sum of its proper divisors (37817052).

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

21211428 is a wasteful number, since it uses less digits than its factorization.

21211428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11016 (or 11014 counting only the distinct ones).

The product of its digits is 256, while the sum is 21.

The square root of 21211428 is about 4605.5866075887. The cubic root of 21211428 is about 276.8152225526.

The spelling of 21211428 in words is "twenty-one million, two hundred eleven thousand, four hundred twenty-eight".