20977561 has 8 divisors (see below), whose sum is σ = 23040000. Its totient is φ = 18941040.

The previous prime is 20977543. The next prime is 20977571. The reversal of 20977561 is 16577902.

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 20977561 - 2⁵ = 20977529 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20977561.

It is not an unprimeable number, because it can be changed into a prime (20977531) 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, 4761 + ... + 8038.

It is an arithmetic number, because the mean of its divisors is an integer number (2880000).

Almost surely, 2^20977561 is an apocalyptic number.

It is an amenable number.

20977561 is a deficient number, since it is larger than the sum of its proper divisors (2062439).

20977561 is a wasteful number, since it uses less digits than its factorization.

20977561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12959.

The product of its (nonzero) digits is 26460, while the sum is 37.

The square root of 20977561 is about 4580.1267449711. The cubic root of 20977561 is about 275.7941167451.

The spelling of 20977561 in words is "twenty million, nine hundred seventy-seven thousand, five hundred sixty-one".