21957649 has 8 divisors (see below), whose sum is σ = 25678400. Its totient is φ = 18382896.

The previous prime is 21957631. The next prime is 21957671. The reversal of 21957649 is 94675912.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21957649 - 2¹⁷ = 21826577 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (43).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21957619) 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, 36174 + ... + 36775.

It is an arithmetic number, because the mean of its divisors is an integer number (3209800).

Almost surely, 2^21957649 is an apocalyptic number.

It is an amenable number.

21957649 is a deficient number, since it is larger than the sum of its proper divisors (3720751).

21957649 is an equidigital number, since it uses as much as digits as its factorization.

21957649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72999.

The product of its digits is 136080, while the sum is 43.

The square root of 21957649 is about 4685.8989532426. The cubic root of 21957649 is about 280.0240157972.

The spelling of 21957649 in words is "twenty-one million, nine hundred fifty-seven thousand, six hundred forty-nine".