21621953091 has 16 divisors (see below), whose sum is σ = 30262869504. Its totient is φ = 13705342464.

The previous prime is 21621952997. The next prime is 21621953131. The reversal of 21621953091 is 19035912612.

It is not a de Polignac number, because 21621953091 - 2¹³ = 21621944899 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21621993091) 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 15 ways as a sum of consecutive naturals, for example, 926686 + ... + 949731.

It is an arithmetic number, because the mean of its divisors is an integer number (1891429344).

Almost surely, 2^21621953091 is an apocalyptic number.

21621953091 is a deficient number, since it is larger than the sum of its proper divisors (8640916413).

21621953091 is a wasteful number, since it uses less digits than its factorization.

21621953091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1876610.

The product of its (nonzero) digits is 29160, while the sum is 39.

It can be divided in two parts, 2162 and 1953091, that added together give a triangular number (1955253 = T₁₉₇₇).

The spelling of 21621953091 in words is "twenty-one billion, six hundred twenty-one million, nine hundred fifty-three thousand, ninety-one".