20157661 has 4 divisors (see below), whose sum is σ = 20171772. Its totient is φ = 20143552.

The previous prime is 20157659. The next prime is 20157677. The reversal of 20157661 is 16675102.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 11689561 + 8468100 = 3419^2 + 2910^2 .

It is a cyclic number.

It is not a de Polignac number, because 20157661 - 2¹ = 20157659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20157061) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4636 + ... + 7861.

It is an arithmetic number, because the mean of its divisors is an integer number (5042943).

Almost surely, 2^20157661 is an apocalyptic number.

It is an amenable number.

20157661 is a deficient number, since it is larger than the sum of its proper divisors (14111).

20157661 is a wasteful number, since it uses less digits than its factorization.

20157661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14110.

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 20157661 is about 4489.7283882213. The cubic root of 20157661 is about 272.1531585885.

The spelling of 20157661 in words is "twenty million, one hundred fifty-seven thousand, six hundred sixty-one".