20961515 has 8 divisors (see below), whose sum is σ = 25265040. Its totient is φ = 16695072.

The previous prime is 20961467. The next prime is 20961517. The reversal of 20961515 is 51516902.

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

It is a cyclic number.

It is not a de Polignac number, because 20961515 - 2²⁰ = 19912939 is a prime.

It is a super-2 number, since 2×20961515² = 878770222190450, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (20961517) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8009 + ... + 10298.

It is an arithmetic number, because the mean of its divisors is an integer number (3158130).

Almost surely, 2^20961515 is an apocalyptic number.

20961515 is a deficient number, since it is larger than the sum of its proper divisors (4303525).

20961515 is a wasteful number, since it uses less digits than its factorization.

20961515 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18541.

The product of its (nonzero) digits is 2700, while the sum is 29.

The square root of 20961515 is about 4578.3747116198. The cubic root of 20961515 is about 275.7237793463.

The spelling of 20961515 in words is "twenty million, nine hundred sixty-one thousand, five hundred fifteen".