21155001405 has 32 divisors (see below), whose sum is σ = 34640887680. Its totient is φ = 11021429760.

The previous prime is 21155001383. The next prime is 21155001419. The reversal of 21155001405 is 50410055112.

It is not a de Polignac number, because 21155001405 - 2¹⁴ = 21154985021 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 15345 + ... + 206265.

It is an arithmetic number, because the mean of its divisors is an integer number (1082527740).

Almost surely, 2^21155001405 is an apocalyptic number.

It is an amenable number.

21155001405 is a deficient number, since it is larger than the sum of its proper divisors (13485886275).

21155001405 is a wasteful number, since it uses less digits than its factorization.

21155001405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 191101.

The product of its (nonzero) digits is 1000, while the sum is 24.

Adding to 21155001405 its reverse (50410055112), we get a palindrome (71565056517).

The spelling of 21155001405 in words is "twenty-one billion, one hundred fifty-five million, one thousand, four hundred five".