21123401505 has 16 divisors (see below), whose sum is σ = 33809892480. Its totient is φ = 11261664128.

The previous prime is 21123401471. The next prime is 21123401543. The reversal of 21123401505 is 50510432112.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21123401505 - 2¹⁴ = 21123385121 is a prime.

It is a super-2 number, since 2×21123401505² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 217077 + ... + 298946.

It is an arithmetic number, because the mean of its divisors is an integer number (2113118280).

Almost surely, 2^21123401505 is an apocalyptic number.

It is an amenable number.

21123401505 is a deficient number, since it is larger than the sum of its proper divisors (12686490975).

21123401505 is a wasteful number, since it uses less digits than its factorization.

21123401505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 518760.

The product of its (nonzero) digits is 1200, while the sum is 24.

Adding to 21123401505 its reverse (50510432112), we get a palindrome (71633833617).

The spelling of 21123401505 in words is "twenty-one billion, one hundred twenty-three million, four hundred one thousand, five hundred five".