21553029931 has 4 divisors (see below), whose sum is σ = 21578298112. Its totient is φ = 21527761752.

The previous prime is 21553029787. The next prime is 21553029973. The reversal of 21553029931 is 13992035512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21553029931 - 2²¹ = 21550932779 is a prime.

It is a super-2 number, since 2×21553029931² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21553029991) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12632811 + ... + 12634516.

It is an arithmetic number, because the mean of its divisors is an integer number (5394574528).

Almost surely, 2^21553029931 is an apocalyptic number.

21553029931 is a deficient number, since it is larger than the sum of its proper divisors (25268181).

21553029931 is an equidigital number, since it uses as much as digits as its factorization.

21553029931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25268180.

The product of its (nonzero) digits is 72900, while the sum is 40.

The spelling of 21553029931 in words is "twenty-one billion, five hundred fifty-three million, twenty-nine thousand, nine hundred thirty-one".