21531123550 has 24 divisors (see below), whose sum is σ = 40052990016. Its totient is φ = 8611352640.

The previous prime is 21531123547. The next prime is 21531123557. The reversal of 21531123550 is 5532113512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21531123557) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 452179 + ... + 497521.

It is an arithmetic number, because the mean of its divisors is an integer number (1668874584).

Almost surely, 2^21531123550 is an apocalyptic number.

21531123550 is a deficient number, since it is larger than the sum of its proper divisors (18521866466).

21531123550 is a wasteful number, since it uses less digits than its factorization.

21531123550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54852 (or 54847 counting only the distinct ones).

The product of its (nonzero) digits is 4500, while the sum is 28.

The spelling of 21531123550 in words is "twenty-one billion, five hundred thirty-one million, one hundred twenty-three thousand, five hundred fifty".