21121031544 has 16 divisors (see below), whose sum is σ = 52802578920. Its totient is φ = 7040343840.

The previous prime is 21121031539. The next prime is 21121031549. The reversal of 21121031544 is 44513012112.

It is an interprime number because it is at equal distance from previous prime (21121031539) and next prime (21121031549).

It is a Harshad number since it is a multiple of its sum of digits (24), and also a Moran number because the ratio is a prime number: 880042981 = 21121031544 / (2 + 1 + 1 + 2 + 1 + 0 + 3 + 1 + 5 + 4 + 4).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121031549) 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, 440021467 + ... + 440021514.

Almost surely, 2^21121031544 is an apocalyptic number.

21121031544 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21121031544 is an abundant number, since it is smaller than the sum of its proper divisors (31681547376).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21121031544 is a wasteful number, since it uses less digits than its factorization.

21121031544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 880042990 (or 880042986 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 24.

Adding to 21121031544 its reverse (44513012112), we get a palindrome (65634043656).

The spelling of 21121031544 in words is "twenty-one billion, one hundred twenty-one million, thirty-one thousand, five hundred forty-four".