21789657 has 6 divisors (see below), whose sum is σ = 31473962. Its totient is φ = 14526432.

The previous prime is 21789653. The next prime is 21789661. The reversal of 21789657 is 75698712.

It is an interprime number because it is at equal distance from previous prime (21789653) and next prime (21789661).

It can be written as a sum of positive squares in only one way, i.e., 14930496 + 6859161 = 3864^2 + 2619^2 .

It is not a de Polignac number, because 21789657 - 2² = 21789653 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21789653) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1210528 + ... + 1210545.

Almost surely, 2^21789657 is an apocalyptic number.

It is an amenable number.

21789657 is a deficient number, since it is larger than the sum of its proper divisors (9684305).

21789657 is a wasteful number, since it uses less digits than its factorization.

21789657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2421079 (or 2421076 counting only the distinct ones).

The product of its digits is 211680, while the sum is 45.

The square root of 21789657 is about 4667.9392669571. The cubic root of 21789657 is about 279.3080576212.

The spelling of 21789657 in words is "twenty-one million, seven hundred eighty-nine thousand, six hundred fifty-seven".