21165651550 has 24 divisors (see below), whose sum is σ = 39842434296. Its totient is φ = 8364255840.

The previous prime is 21165651547. The next prime is 21165651553. The reversal of 21165651550 is 5515656112.

It is an interprime number because it is at equal distance from previous prime (21165651547) and next prime (21165651553).

It is a hoax number, since the sum of its digits (37) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21165651553) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2545929 + ... + 2554228.

It is an arithmetic number, because the mean of its divisors is an integer number (1660101429).

Almost surely, 2^21165651550 is an apocalyptic number.

21165651550 is a deficient number, since it is larger than the sum of its proper divisors (18676782746).

21165651550 is a wasteful number, since it uses less digits than its factorization.

21165651550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5100252 (or 5100247 counting only the distinct ones).

The product of its (nonzero) digits is 45000, while the sum is 37.

The spelling of 21165651550 in words is "twenty-one billion, one hundred sixty-five million, six hundred fifty-one thousand, five hundred fifty".