21405150391 has 2 divisors, whose sum is σ = 21405150392. Its totient is φ = 21405150390.

The previous prime is 21405150337. The next prime is 21405150427. The reversal of 21405150391 is 19305150412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21405150391 - 2¹⁷ = 21405019319 is a prime.

It is a super-2 number, since 2×21405150391² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21405150791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10702575195 + 10702575196.

It is an arithmetic number, because the mean of its divisors is an integer number (10702575196).

Almost surely, 2^21405150391 is an apocalyptic number.

21405150391 is a deficient number, since it is larger than the sum of its proper divisors (1).

21405150391 is an equidigital number, since it uses as much as digits as its factorization.

21405150391 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5400, while the sum is 31.

The spelling of 21405150391 in words is "twenty-one billion, four hundred five million, one hundred fifty thousand, three hundred ninety-one".