21971028 has 24 divisors (see below), whose sum is σ = 51393888. Its totient is φ = 7305376.

The previous prime is 21971023. The next prime is 21971057. The reversal of 21971028 is 82017912.

It is a junction number, because it is equal to n+sod(n) for n = 21970986 and 21971004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21971023) 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, 3250 + ... + 7382.

It is an arithmetic number, because the mean of its divisors is an integer number (2141412).

Almost surely, 2^21971028 is an apocalyptic number.

It is an amenable number.

21971028 is an abundant number, since it is smaller than the sum of its proper divisors (29422860).

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

21971028 is a wasteful number, since it uses less digits than its factorization.

21971028 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4583 (or 4581 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 21971028 is about 4687.3263167823. The cubic root of 21971028 is about 280.0808779967.

The spelling of 21971028 in words is "twenty-one million, nine hundred seventy-one thousand, twenty-eight".