21615425421 has 16 divisors (see below), whose sum is σ = 30546759168. Its totient is φ = 13548902400.

The previous prime is 21615425417. The next prime is 21615425473. The reversal of 21615425421 is 12452451612.

It is a happy number.

It is not a de Polignac number, because 21615425421 - 2² = 21615425417 is a prime.

It is a super-2 number, since 2×21615425421² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21615424421) 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, 163300 + ... + 264381.

It is an arithmetic number, because the mean of its divisors is an integer number (1909172448).

Almost surely, 2^21615425421 is an apocalyptic number.

It is an amenable number.

21615425421 is a deficient number, since it is larger than the sum of its proper divisors (8931333747).

21615425421 is a wasteful number, since it uses less digits than its factorization.

21615425421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 428692.

The product of its digits is 19200, while the sum is 33.

The spelling of 21615425421 in words is "twenty-one billion, six hundred fifteen million, four hundred twenty-five thousand, four hundred twenty-one".