21701628 has 144 divisors (see below), whose sum is σ = 64562400. Its totient is φ = 6289920.

The previous prime is 21701623. The next prime is 21701651. The reversal of 21701628 is 82610712.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21701621) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 529288 + ... + 529328.

It is an arithmetic number, because the mean of its divisors is an integer number (448350).

Almost surely, 2^21701628 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 21701628, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32281200).

21701628 is an abundant number, since it is smaller than the sum of its proper divisors (42860772).

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

21701628 is a wasteful number, since it uses less digits than its factorization.

21701628 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 109 (or 88 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 21701628 is about 4658.5006171514. The cubic root of 21701628 is about 278.9314203045.

The spelling of 21701628 in words is "twenty-one million, seven hundred one thousand, six hundred twenty-eight".