21891550 has 24 divisors (see below), whose sum is σ = 40863456. Its totient is φ = 8725440.

The previous prime is 21891539. The next prime is 21891557. The reversal of 21891550 is 5519812.

It is a super-2 number, since 2×21891550² = 958479922805000, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21891557) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 17754 + ... + 18946.

It is an arithmetic number, because the mean of its divisors is an integer number (1702644).

Almost surely, 2^21891550 is an apocalyptic number.

21891550 is a deficient number, since it is larger than the sum of its proper divisors (18971906).

21891550 is a wasteful number, since it uses less digits than its factorization.

21891550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1572 (or 1567 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 31.

The square root of 21891550 is about 4678.8406683707. The cubic root of 21891550 is about 279.7427484149.

The spelling of 21891550 in words is "twenty-one million, eight hundred ninety-one thousand, five hundred fifty".