21180391557 has 16 divisors (see below), whose sum is σ = 30588676608. Its totient is φ = 12958741440.

The previous prime is 21180391553. The next prime is 21180391567. The reversal of 21180391557 is 75519308112.

It is not a de Polignac number, because 21180391557 - 2² = 21180391553 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21180391553) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1562869 + ... + 1576362.

It is an arithmetic number, because the mean of its divisors is an integer number (1911792288).

Almost surely, 2^21180391557 is an apocalyptic number.

It is an amenable number.

21180391557 is a deficient number, since it is larger than the sum of its proper divisors (9408285051).

21180391557 is a wasteful number, since it uses less digits than its factorization.

21180391557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3139420.

The product of its (nonzero) digits is 75600, while the sum is 42.

Adding to 21180391557 its reverse (75519308112), we get a palindrome (96699699669).

The spelling of 21180391557 in words is "twenty-one billion, one hundred eighty million, three hundred ninety-one thousand, five hundred fifty-seven".