21591628 has 6 divisors (see below), whose sum is σ = 37785356. Its totient is φ = 10795812.

The previous prime is 21591623. The next prime is 21591629. The reversal of 21591628 is 82619512.

It is a junction number, because it is equal to n+sod(n) for n = 21591593 and 21591602.

It is not an unprimeable number, because it can be changed into a prime (21591623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2698950 + ... + 2698957.

Almost surely, 2^21591628 is an apocalyptic number.

It is an amenable number.

21591628 is a deficient number, since it is larger than the sum of its proper divisors (16193728).

21591628 is a wasteful number, since it uses less digits than its factorization.

21591628 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5397911 (or 5397909 counting only the distinct ones).

The product of its digits is 8640, while the sum is 34.

The square root of 21591628 is about 4646.6792443637. The cubic root of 21591628 is about 278.4593444581.

The spelling of 21591628 in words is "twenty-one million, five hundred ninety-one thousand, six hundred twenty-eight".