21958649 has 8 divisors (see below), whose sum is σ = 22614408. Its totient is φ = 21306240.

The previous prime is 21958639. The next prime is 21958691. The reversal of 21958649 is 94685912.

It can be written as a sum of positive squares in 4 ways, for example, as 4276624 + 17682025 = 2068^2 + 4205^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21958649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21958609) 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, 19469 + ... + 20565.

It is an arithmetic number, because the mean of its divisors is an integer number (2826801).

Almost surely, 2^21958649 is an apocalyptic number.

It is an amenable number.

21958649 is a deficient number, since it is larger than the sum of its proper divisors (655759).

21958649 is a wasteful number, since it uses less digits than its factorization.

21958649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1675.

The product of its digits is 155520, while the sum is 44.

The square root of 21958649 is about 4686.0056551396. The cubic root of 21958649 is about 280.0282667041.

The spelling of 21958649 in words is "twenty-one million, nine hundred fifty-eight thousand, six hundred forty-nine".