261545621 has 4 divisors (see below), whose sum is σ = 275311200. Its totient is φ = 247780044.

The previous prime is 261545593. The next prime is 261545633. The reversal of 261545621 is 126545162.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 261545621 - 2²⁶ = 194436757 is a prime.

It is a super-2 number, since 2×261545621² = 136812223728551282, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261545681) 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, 6882761 + ... + 6882798.

It is an arithmetic number, because the mean of its divisors is an integer number (68827800).

Almost surely, 2^261545621 is an apocalyptic number.

It is an amenable number.

261545621 is a deficient number, since it is larger than the sum of its proper divisors (13765579).

261545621 is a wasteful number, since it uses less digits than its factorization.

261545621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13765578.

The product of its digits is 14400, while the sum is 32.

The square root of 261545621 is about 16172.3721512956. The cubic root of 261545621 is about 639.5126669337.

The spelling of 261545621 in words is "two hundred sixty-one million, five hundred forty-five thousand, six hundred twenty-one".