15956646421 has 8 divisors (see below), whose sum is σ = 16029286688. Its totient is φ = 15884154000.

The previous prime is 15956646401. The next prime is 15956646457. The reversal of 15956646421 is 12464665951.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a 3-Lehmer number, since φ(15956646421) divides (15956646421-1)³.

It is a cyclic number.

It is a Carmichael number.

It is not a de Polignac number, because 15956646421 - 2⁵ = 15956646389 is a prime.

It is a super-2 number, since 2×15956646421² (a number of 21 digits) contains 22 as substring.

It is a deceptive number, since it divides R_15956646420.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15956646401) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 182326 + ... + 255256.

It is an arithmetic number, because the mean of its divisors is an integer number (2003660836).

It is a Poulet number, since it divides 2^15956646420-1.

Almost surely, 2^15956646421 is an apocalyptic number.

15956646421 is the 72931-st octagonal number.

It is an amenable number.

15956646421 is a deficient number, since it is larger than the sum of its proper divisors (72640267).

15956646421 is an equidigital number, since it uses as much as digits as its factorization.

15956646421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73923.

The product of its digits is 1555200, while the sum is 49.

The spelling of 15956646421 in words is "fifteen billion, nine hundred fifty-six million, six hundred forty-six thousand, four hundred twenty-one".